Regen all docs. (#700)

* Stop recursing if discovery == {}

* Generate docs with 'make docs'.
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+<style>
+
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+  margin: 0;
+  padding: 0;
+  border: 0;
+  font-weight: inherit;
+  font-style: inherit;
+  font-size: 100%;
+  font-family: inherit;
+  vertical-align: baseline;
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+  font-family: Monaco, 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Lucida Console', monospace;
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+  margin-top: 0.5em;
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+  margin-left: 2 em;
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+.method  {
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+.details {
+  font-weight: bold;
+  font-size: 14px;
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+</style>
+
+<h1><a href="composer_v1beta1.html">Cloud Composer API</a> . <a href="composer_v1beta1.projects.html">projects</a> . <a href="composer_v1beta1.projects.locations.html">locations</a> . <a href="composer_v1beta1.projects.locations.imageVersions.html">imageVersions</a></h1>
+<h2>Instance Methods</h2>
+<p class="toc_element">
+  <code><a href="#list">list(parent, pageToken=None, x__xgafv=None, pageSize=None)</a></code></p>
+<p class="firstline">List ImageVersions for provided location.</p>
+<p class="toc_element">
+  <code><a href="#list_next">list_next(previous_request, previous_response)</a></code></p>
+<p class="firstline">Retrieves the next page of results.</p>
+<h3>Method Details</h3>
+<div class="method">
+    <code class="details" id="list">list(parent, pageToken=None, x__xgafv=None, pageSize=None)</code>
+  <pre>List ImageVersions for provided location.
+
+Args:
+  parent: string, List ImageVersions in the given project and location, in the form:
+"projects/{projectId}/locations/{locationId}" (required)
+  pageToken: string, The next_page_token value returned from a previous List request, if any.
+  x__xgafv: string, V1 error format.
+    Allowed values
+      1 - v1 error format
+      2 - v2 error format
+  pageSize: integer, The maximum number of image_versions to return.
+
+Returns:
+  An object of the form:
+
+    { # The ImageVersions in a project and location.
+    "nextPageToken": "A String", # The page token used to query for the next page if one exists.
+    "imageVersions": [ # The list of supported ImageVersions in a location.
+      { # Image Version information
+        "imageVersionId": "A String", # The string identifier of the ImageVersion, in the form:
+            # "composer-x.y.z-airflow-a.b(.c)"
+        "supportedPythonVersions": [ # supported python versions
+          "A String",
+        ],
+        "isDefault": True or False, # Whether this is the default ImageVersion used by Composer during
+            # environment creation if no input ImageVersion is specified.
+      },
+    ],
+  }</pre>
+</div>
+
+<div class="method">
+    <code class="details" id="list_next">list_next(previous_request, previous_response)</code>
+  <pre>Retrieves the next page of results.
+
+Args:
+  previous_request: The request for the previous page. (required)
+  previous_response: The response from the request for the previous page. (required)
+
+Returns:
+  A request object that you can call 'execute()' on to request the next
+  page. Returns None if there are no more items in the collection.
+    </pre>
+</div>
+
+</body></html>
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