blacken api_core and core (#6668)

* blacken api_core and core
diff --git a/tests/unit/operations_v1/test_operations_client.py b/tests/unit/operations_v1/test_operations_client.py
index 69d4dfc..cc57461 100644
--- a/tests/unit/operations_v1/test_operations_client.py
+++ b/tests/unit/operations_v1/test_operations_client.py
@@ -22,12 +22,12 @@
 def test_get_operation():
     channel = grpc_helpers.ChannelStub()
     client = operations_v1.OperationsClient(channel)
-    channel.GetOperation.response = operations_pb2.Operation(name='meep')
+    channel.GetOperation.response = operations_pb2.Operation(name="meep")
 
-    response = client.get_operation('name')
+    response = client.get_operation("name")
 
     assert len(channel.GetOperation.requests) == 1
-    assert channel.GetOperation.requests[0].name == 'name'
+    assert channel.GetOperation.requests[0].name == "name"
     assert response == channel.GetOperation.response
 
 
@@ -35,13 +35,13 @@
     channel = grpc_helpers.ChannelStub()
     client = operations_v1.OperationsClient(channel)
     operations = [
-        operations_pb2.Operation(name='1'),
-        operations_pb2.Operation(name='2')]
-    list_response = operations_pb2.ListOperationsResponse(
-        operations=operations)
+        operations_pb2.Operation(name="1"),
+        operations_pb2.Operation(name="2"),
+    ]
+    list_response = operations_pb2.ListOperationsResponse(operations=operations)
     channel.ListOperations.response = list_response
 
-    response = client.list_operations('name', 'filter')
+    response = client.list_operations("name", "filter")
 
     assert isinstance(response, page_iterator.Iterator)
     assert list(response) == operations
@@ -49,8 +49,8 @@
     assert len(channel.ListOperations.requests) == 1
     request = channel.ListOperations.requests[0]
     assert isinstance(request, operations_pb2.ListOperationsRequest)
-    assert request.name == 'name'
-    assert request.filter == 'filter'
+    assert request.name == "name"
+    assert request.filter == "filter"
 
 
 def test_delete_operation():
@@ -58,10 +58,10 @@
     client = operations_v1.OperationsClient(channel)
     channel.DeleteOperation.response = empty_pb2.Empty()
 
-    client.delete_operation('name')
+    client.delete_operation("name")
 
     assert len(channel.DeleteOperation.requests) == 1
-    assert channel.DeleteOperation.requests[0].name == 'name'
+    assert channel.DeleteOperation.requests[0].name == "name"
 
 
 def test_cancel_operation():
@@ -69,7 +69,7 @@
     client = operations_v1.OperationsClient(channel)
     channel.CancelOperation.response = empty_pb2.Empty()
 
-    client.cancel_operation('name')
+    client.cancel_operation("name")
 
     assert len(channel.CancelOperation.requests) == 1
-    assert channel.CancelOperation.requests[0].name == 'name'
+    assert channel.CancelOperation.requests[0].name == "name"