Release v1.6.0 (#324)

* Update version and changelog for v1.6.0
* Update docs
diff --git a/docs/dyn/compute_beta.instances.html b/docs/dyn/compute_beta.instances.html
index 9d6834e..2b85832 100644
--- a/docs/dyn/compute_beta.instances.html
+++ b/docs/dyn/compute_beta.instances.html
@@ -129,6 +129,9 @@
   <code><a href="#setScheduling">setScheduling(project, zone, instance, body)</a></code></p>
 <p class="firstline">Sets an instance's scheduling options.</p>
 <p class="toc_element">
+  <code><a href="#setServiceAccount">setServiceAccount(project, zone, instance, body)</a></code></p>
+<p class="firstline">Sets the service account on the instance.</p>
+<p class="toc_element">
   <code><a href="#setTags">setTags(project, zone, instance, body)</a></code></p>
 <p class="firstline">Sets tags for the specified instance to the data included in the request.</p>
 <p class="toc_element">
@@ -210,7 +213,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -317,7 +320,7 @@
                       # - projects/project/zones/zone/diskTypes/diskType
                       # - zones/zone/diskTypes/diskType  Note that for InstanceTemplate, this is the name of the disk type, not URL.
                   "diskSizeGb": "A String", # Specifies the size of the disk in base-2 GB.
-                  "sourceImage": "A String", # The source image used to create this disk. If the source image is deleted, this field will not be set.
+                  "sourceImage": "A String", # The source image to create this disk. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
                       #
                       # To create a disk with one of the public operating system images, specify the image by its family name. For example, specify family/debian-8 to use the latest Debian 8 image:
                       #
@@ -334,6 +337,8 @@
                       # You can also specify a private image by its image family, which returns the latest version of the image in that family. Replace the image name with family/family-name:
                       #
                       # global/images/family/my-private-family
+                      #
+                      # If the source image is deleted later, this field will not be set.
                   "diskStorageType": "A String", # [Deprecated] Storage type of the disk.
                 },
                 "autoDelete": True or False, # Specifies whether the disk will be auto-deleted when the instance is deleted (but not when the disk is detached from the instance).
@@ -345,7 +350,11 @@
                 "mode": "A String", # The mode in which to attach this disk, either READ_WRITE or READ_ONLY. If not specified, the default is to attach the disk in READ_WRITE mode.
                 "interface": "A String", # Specifies the disk interface to use for attaching this disk, which is either SCSI or NVME. The default is SCSI. Persistent disks must always use SCSI and the request will fail if you attempt to attach a persistent disk in any other format than SCSI. Local SSDs can use either NVME or SCSI. For performance characteristics of SCSI over NVMe, see Local SSD performance.
                 "type": "A String", # Specifies the type of the disk, either SCRATCH or PERSISTENT. If not specified, the default is PERSISTENT.
-                "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. This field is only applicable for persistent disks. Note that for InstanceTemplate, it is just disk name, not URL for the disk.
+                "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
+                    #
+                    # If desired, you can also attach existing non-root persistent disks using this property. This field is only applicable for persistent disks.
+                    #
+                    # Note that for InstanceTemplate, specify the disk name, not the URL for the disk.
               },
             ],
             "name": "A String", # The name of the resource, provided by the client when initially creating the resource. The resource name must be 1-63 characters long, and comply with RFC1035. Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])? which means the first character must be a lowercase letter, and all following characters must be a dash, lowercase letter, or digit, except the last character, which cannot be a dash.
@@ -508,7 +517,7 @@
         # - projects/project/zones/zone/diskTypes/diskType
         # - zones/zone/diskTypes/diskType  Note that for InstanceTemplate, this is the name of the disk type, not URL.
     "diskSizeGb": "A String", # Specifies the size of the disk in base-2 GB.
-    "sourceImage": "A String", # The source image used to create this disk. If the source image is deleted, this field will not be set.
+    "sourceImage": "A String", # The source image to create this disk. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
         #
         # To create a disk with one of the public operating system images, specify the image by its family name. For example, specify family/debian-8 to use the latest Debian 8 image:
         #
@@ -525,6 +534,8 @@
         # You can also specify a private image by its image family, which returns the latest version of the image in that family. Replace the image name with family/family-name:
         #
         # global/images/family/my-private-family
+        #
+        # If the source image is deleted later, this field will not be set.
     "diskStorageType": "A String", # [Deprecated] Storage type of the disk.
   },
   "autoDelete": True or False, # Specifies whether the disk will be auto-deleted when the instance is deleted (but not when the disk is detached from the instance).
@@ -536,7 +547,11 @@
   "mode": "A String", # The mode in which to attach this disk, either READ_WRITE or READ_ONLY. If not specified, the default is to attach the disk in READ_WRITE mode.
   "interface": "A String", # Specifies the disk interface to use for attaching this disk, which is either SCSI or NVME. The default is SCSI. Persistent disks must always use SCSI and the request will fail if you attempt to attach a persistent disk in any other format than SCSI. Local SSDs can use either NVME or SCSI. For performance characteristics of SCSI over NVMe, see Local SSD performance.
   "type": "A String", # Specifies the type of the disk, either SCRATCH or PERSISTENT. If not specified, the default is PERSISTENT.
-  "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. This field is only applicable for persistent disks. Note that for InstanceTemplate, it is just disk name, not URL for the disk.
+  "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
+      # 
+      # If desired, you can also attach existing non-root persistent disks using this property. This field is only applicable for persistent disks.
+      # 
+      # Note that for InstanceTemplate, specify the disk name, not the URL for the disk.
 }
 
 
@@ -586,7 +601,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -645,7 +660,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -706,7 +721,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -766,7 +781,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -854,7 +869,7 @@
               # - projects/project/zones/zone/diskTypes/diskType
               # - zones/zone/diskTypes/diskType  Note that for InstanceTemplate, this is the name of the disk type, not URL.
           "diskSizeGb": "A String", # Specifies the size of the disk in base-2 GB.
-          "sourceImage": "A String", # The source image used to create this disk. If the source image is deleted, this field will not be set.
+          "sourceImage": "A String", # The source image to create this disk. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
               #
               # To create a disk with one of the public operating system images, specify the image by its family name. For example, specify family/debian-8 to use the latest Debian 8 image:
               #
@@ -871,6 +886,8 @@
               # You can also specify a private image by its image family, which returns the latest version of the image in that family. Replace the image name with family/family-name:
               #
               # global/images/family/my-private-family
+              #
+              # If the source image is deleted later, this field will not be set.
           "diskStorageType": "A String", # [Deprecated] Storage type of the disk.
         },
         "autoDelete": True or False, # Specifies whether the disk will be auto-deleted when the instance is deleted (but not when the disk is detached from the instance).
@@ -882,7 +899,11 @@
         "mode": "A String", # The mode in which to attach this disk, either READ_WRITE or READ_ONLY. If not specified, the default is to attach the disk in READ_WRITE mode.
         "interface": "A String", # Specifies the disk interface to use for attaching this disk, which is either SCSI or NVME. The default is SCSI. Persistent disks must always use SCSI and the request will fail if you attempt to attach a persistent disk in any other format than SCSI. Local SSDs can use either NVME or SCSI. For performance characteristics of SCSI over NVMe, see Local SSD performance.
         "type": "A String", # Specifies the type of the disk, either SCRATCH or PERSISTENT. If not specified, the default is PERSISTENT.
-        "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. This field is only applicable for persistent disks. Note that for InstanceTemplate, it is just disk name, not URL for the disk.
+        "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
+            #
+            # If desired, you can also attach existing non-root persistent disks using this property. This field is only applicable for persistent disks.
+            #
+            # Note that for InstanceTemplate, specify the disk name, not the URL for the disk.
       },
     ],
     "name": "A String", # The name of the resource, provided by the client when initially creating the resource. The resource name must be 1-63 characters long, and comply with RFC1035. Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])? which means the first character must be a lowercase letter, and all following characters must be a dash, lowercase letter, or digit, except the last character, which cannot be a dash.
@@ -1057,7 +1078,7 @@
             # - projects/project/zones/zone/diskTypes/diskType
             # - zones/zone/diskTypes/diskType  Note that for InstanceTemplate, this is the name of the disk type, not URL.
         "diskSizeGb": "A String", # Specifies the size of the disk in base-2 GB.
-        "sourceImage": "A String", # The source image used to create this disk. If the source image is deleted, this field will not be set.
+        "sourceImage": "A String", # The source image to create this disk. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
             #
             # To create a disk with one of the public operating system images, specify the image by its family name. For example, specify family/debian-8 to use the latest Debian 8 image:
             #
@@ -1074,6 +1095,8 @@
             # You can also specify a private image by its image family, which returns the latest version of the image in that family. Replace the image name with family/family-name:
             #
             # global/images/family/my-private-family
+            #
+            # If the source image is deleted later, this field will not be set.
         "diskStorageType": "A String", # [Deprecated] Storage type of the disk.
       },
       "autoDelete": True or False, # Specifies whether the disk will be auto-deleted when the instance is deleted (but not when the disk is detached from the instance).
@@ -1085,7 +1108,11 @@
       "mode": "A String", # The mode in which to attach this disk, either READ_WRITE or READ_ONLY. If not specified, the default is to attach the disk in READ_WRITE mode.
       "interface": "A String", # Specifies the disk interface to use for attaching this disk, which is either SCSI or NVME. The default is SCSI. Persistent disks must always use SCSI and the request will fail if you attempt to attach a persistent disk in any other format than SCSI. Local SSDs can use either NVME or SCSI. For performance characteristics of SCSI over NVMe, see Local SSD performance.
       "type": "A String", # Specifies the type of the disk, either SCRATCH or PERSISTENT. If not specified, the default is PERSISTENT.
-      "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. This field is only applicable for persistent disks. Note that for InstanceTemplate, it is just disk name, not URL for the disk.
+      "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
+          #
+          # If desired, you can also attach existing non-root persistent disks using this property. This field is only applicable for persistent disks.
+          #
+          # Note that for InstanceTemplate, specify the disk name, not the URL for the disk.
     },
   ],
   "name": "A String", # The name of the resource, provided by the client when initially creating the resource. The resource name must be 1-63 characters long, and comply with RFC1035. Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])? which means the first character must be a lowercase letter, and all following characters must be a dash, lowercase letter, or digit, except the last character, which cannot be a dash.
@@ -1201,7 +1228,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1307,7 +1334,7 @@
                   # - projects/project/zones/zone/diskTypes/diskType
                   # - zones/zone/diskTypes/diskType  Note that for InstanceTemplate, this is the name of the disk type, not URL.
               "diskSizeGb": "A String", # Specifies the size of the disk in base-2 GB.
-              "sourceImage": "A String", # The source image used to create this disk. If the source image is deleted, this field will not be set.
+              "sourceImage": "A String", # The source image to create this disk. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
                   #
                   # To create a disk with one of the public operating system images, specify the image by its family name. For example, specify family/debian-8 to use the latest Debian 8 image:
                   #
@@ -1324,6 +1351,8 @@
                   # You can also specify a private image by its image family, which returns the latest version of the image in that family. Replace the image name with family/family-name:
                   #
                   # global/images/family/my-private-family
+                  #
+                  # If the source image is deleted later, this field will not be set.
               "diskStorageType": "A String", # [Deprecated] Storage type of the disk.
             },
             "autoDelete": True or False, # Specifies whether the disk will be auto-deleted when the instance is deleted (but not when the disk is detached from the instance).
@@ -1335,7 +1364,11 @@
             "mode": "A String", # The mode in which to attach this disk, either READ_WRITE or READ_ONLY. If not specified, the default is to attach the disk in READ_WRITE mode.
             "interface": "A String", # Specifies the disk interface to use for attaching this disk, which is either SCSI or NVME. The default is SCSI. Persistent disks must always use SCSI and the request will fail if you attempt to attach a persistent disk in any other format than SCSI. Local SSDs can use either NVME or SCSI. For performance characteristics of SCSI over NVMe, see Local SSD performance.
             "type": "A String", # Specifies the type of the disk, either SCRATCH or PERSISTENT. If not specified, the default is PERSISTENT.
-            "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. This field is only applicable for persistent disks. Note that for InstanceTemplate, it is just disk name, not URL for the disk.
+            "source": "A String", # Specifies a valid partial or full URL to an existing Persistent Disk resource. When creating a new instance, one of initializeParams.sourceImage or disks.source is required.
+                #
+                # If desired, you can also attach existing non-root persistent disks using this property. This field is only applicable for persistent disks.
+                #
+                # Note that for InstanceTemplate, specify the disk name, not the URL for the disk.
           },
         ],
         "name": "A String", # The name of the resource, provided by the client when initially creating the resource. The resource name must be 1-63 characters long, and comply with RFC1035. Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])? which means the first character must be a lowercase letter, and all following characters must be a dash, lowercase letter, or digit, except the last character, which cannot be a dash.
@@ -1479,7 +1512,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1540,7 +1573,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1611,7 +1644,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1677,7 +1710,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1750,7 +1783,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1818,7 +1851,76 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
+  }</pre>
+</div>
+
+<div class="method">
+    <code class="details" id="setServiceAccount">setServiceAccount(project, zone, instance, body)</code>
+  <pre>Sets the service account on the instance.
+
+Args:
+  project: string, Project ID for this request. (required)
+  zone: string, The name of the zone for this request. (required)
+  instance: string, Name of the instance resource to start. (required)
+  body: object, The request body. (required)
+    The object takes the form of:
+
+{
+    "scopes": [ # The list of scopes to be made available for this service account.
+      "A String",
+    ],
+    "email": "A String", # Email address of the service account.
+  }
+
+
+Returns:
+  An object of the form:
+
+    { # An Operation resource, used to manage asynchronous API requests.
+    "targetId": "A String", # [Output Only] The unique target ID, which identifies a specific incarnation of the target resource.
+    "clientOperationId": "A String", # [Output Only] Reserved for future use.
+    "creationTimestamp": "A String", # [Output Only] Creation timestamp in RFC3339 text format.
+    "id": "A String", # [Output Only] The unique identifier for the resource. This identifier is defined by the server.
+    "zone": "A String", # [Output Only] The URL of the zone where the operation resides. Only available when performing per-zone operations.
+    "insertTime": "A String", # [Output Only] The time that this operation was requested. This value is in RFC3339 text format.
+    "operationType": "A String", # [Output Only] The type of operation, such as insert, update, or delete, and so on.
+    "httpErrorMessage": "A String", # [Output Only] If the operation fails, this field contains the HTTP error message that was returned, such as NOT FOUND.
+    "progress": 42, # [Output Only] An optional progress indicator that ranges from 0 to 100. There is no requirement that this be linear or support any granularity of operations. This should not be used to guess when the operation will be complete. This number should monotonically increase as the operation progresses.
+    "httpErrorStatusCode": 42, # [Output Only] If the operation fails, this field contains the HTTP error status code that was returned. For example, a 404 means the resource was not found.
+    "statusMessage": "A String", # [Output Only] An optional textual description of the current status of the operation.
+    "status": "A String", # [Output Only] The status of the operation, which can be one of the following: PENDING, RUNNING, or DONE.
+    "description": "A String", # [Output Only] A textual description of the operation, which is set when the operation is created.
+    "warnings": [ # [Output Only] If warning messages are generated during processing of the operation, this field will be populated.
+      {
+        "message": "A String", # [Output Only] A human-readable description of the warning code.
+        "code": "A String", # [Output Only] A warning code, if applicable. For example, Compute Engine returns NO_RESULTS_ON_PAGE if there are no results in the response.
+        "data": [ # [Output Only] Metadata about this warning in key: value format. For example:
+            # "data": [ { "key": "scope", "value": "zones/us-east1-d" }
+          {
+            "value": "A String", # [Output Only] A warning data value corresponding to the key.
+            "key": "A String", # [Output Only] A key that provides more detail on the warning being returned. For example, for warnings where there are no results in a list request for a particular zone, this key might be scope and the key value might be the zone name. Other examples might be a key indicating a deprecated resource and a suggested replacement, or a warning about invalid network settings (for example, if an instance attempts to perform IP forwarding but is not enabled for IP forwarding).
+          },
+        ],
+      },
+    ],
+    "user": "A String", # [Output Only] User who requested the operation, for example: user@example.com.
+    "startTime": "A String", # [Output Only] The time that this operation was started by the server. This value is in RFC3339 text format.
+    "kind": "compute#operation", # [Output Only] Type of the resource. Always compute#operation for Operation resources.
+    "name": "A String", # [Output Only] Name of the resource.
+    "region": "A String", # [Output Only] The URL of the region where the operation resides. Only available when performing regional operations.
+    "error": { # [Output Only] If errors are generated during processing of the operation, this field will be populated.
+      "errors": [ # [Output Only] The array of errors encountered while processing this operation.
+        {
+          "message": "A String", # [Output Only] An optional, human-readable error message.
+          "code": "A String", # [Output Only] The error type identifier for this error.
+          "location": "A String", # [Output Only] Indicates the field in the request that caused the error. This property is optional.
+        },
+      ],
+    },
+    "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
+    "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1889,7 +1991,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -1948,7 +2050,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -2032,7 +2134,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>
 
@@ -2091,7 +2193,7 @@
     },
     "endTime": "A String", # [Output Only] The time that this operation was completed. This value is in RFC3339 text format.
     "selfLink": "A String", # [Output Only] Server-defined URL for the resource.
-    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. If creating a persistent disk snapshot, this points to the persistent disk that the snapshot was created from.
+    "targetLink": "A String", # [Output Only] The URL of the resource that the operation modifies. For operations related to creating a snapshot, this points to the persistent disk that the snapshot was created from.
   }</pre>
 </div>