Pick up fixes in GAPIC generator. (#6491)

Includes fixes from these PRs:

- googleapis/gapic-generator#2407
- googleapis/gapic-generator#2396

google/cloud/bigquery_datatransfer_v1/gapic/data_transfer_service_client.py

@@ -120,7 +120,7 @@ def __init__(self,
                  transport=None,
                  channel=None,
                  credentials=None,
-                 client_config=data_transfer_service_client_config.config,
+                 client_config=None,
                  client_info=None):
         """Constructor.
 
@@ -153,13 +153,20 @@ def __init__(self,
                 your own client library.
         """
         # Raise deprecation warnings for things we want to go away.
-        if client_config:
-            warnings.warn('The `client_config` argument is deprecated.',
-                          PendingDeprecationWarning)
+        if client_config is not None:
+            warnings.warn(
+                'The `client_config` argument is deprecated.',
+                PendingDeprecationWarning,
+                stacklevel=2)
+        else:
+            client_config = data_transfer_service_client_config.config
+
         if channel:
             warnings.warn(
                 'The `channel` argument is deprecated; use '
-                '`transport` instead.', PendingDeprecationWarning)
+                '`transport` instead.',
+                PendingDeprecationWarning,
+                stacklevel=2)
 
         # Instantiate the transport.
         # The transport is responsible for handling serialization and

google/cloud/bigquery_datatransfer_v1/gapic/enums.py

@@ -18,19 +18,6 @@
 import enum
 
 
-class NullValue(enum.IntEnum):
-    """
-    ``NullValue`` is a singleton enumeration to represent the null value for
-    the ``Value`` type union.
-
-    The JSON representation for ``NullValue`` is JSON ``null``.
-
-    Attributes:
-      NULL_VALUE (int): Null value.
-    """
-    NULL_VALUE = 0
-
-
 class TransferType(enum.IntEnum):
     """
     DEPRECATED. Represents data transfer type.
@@ -67,21 +54,17 @@ class TransferState(enum.IntEnum):
     CANCELLED = 6
 
 
-class TransferMessage(object):
-    class MessageSeverity(enum.IntEnum):
-        """
-        Represents data transfer user facing message severity.
+class NullValue(enum.IntEnum):
+    """
+    ``NullValue`` is a singleton enumeration to represent the null value for
+    the ``Value`` type union.
 
-        Attributes:
-          MESSAGE_SEVERITY_UNSPECIFIED (int): No severity specified.
-          INFO (int): Informational message.
-          WARNING (int): Warning message.
-          ERROR (int): Error message.
-        """
-        MESSAGE_SEVERITY_UNSPECIFIED = 0
-        INFO = 1
-        WARNING = 2
-        ERROR = 3
+    The JSON representation for ``NullValue`` is JSON ``null``.
+
+    Attributes:
+      NULL_VALUE (int): Null value.
+    """
+    NULL_VALUE = 0
 
 
 class DataSourceParameter(object):
@@ -153,3 +136,20 @@ class RunAttempt(enum.IntEnum):
         """
         RUN_ATTEMPT_UNSPECIFIED = 0
         LATEST = 1
+
+
+class TransferMessage(object):
+    class MessageSeverity(enum.IntEnum):
+        """
+        Represents data transfer user facing message severity.
+
+        Attributes:
+          MESSAGE_SEVERITY_UNSPECIFIED (int): No severity specified.
+          INFO (int): Informational message.
+          WARNING (int): Warning message.
+          ERROR (int): Error message.
+        """
+        MESSAGE_SEVERITY_UNSPECIFIED = 0
+        INFO = 1
+        WARNING = 2
+        ERROR = 3

google/cloud/bigquery_datatransfer_v1/gapic/transports/data_transfer_service_grpc_transport.py

@@ -62,6 +62,8 @@ def __init__(self,
                 credentials=credentials,
             )
 
+        self._channel = channel
+
         # gRPC uses objects called "stubs" that are bound to the
         # channel and provide a basic method for each RPC.
         self._stubs = {
@@ -92,6 +94,15 @@ def create_channel(cls,
             scopes=cls._OAUTH_SCOPES,
         )
 
+    @property
+    def channel(self):
+        """The gRPC channel used by the transport.
+
+        Returns:
+            grpc.Channel: A gRPC channel object.
+        """
+        return self._channel
+
     @property
     def get_data_source(self):
         """Return the gRPC stub for {$apiMethod.name}.