add imports

Author: ohmayr

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/grpc.py.j2

@@ -44,6 +44,9 @@ from google.longrunning import operations_pb2 # type: ignore
 {% endfilter %}
 from .base import {{ service.name }}Transport, DEFAULT_CLIENT_INFO
 
+import proto
+import google.protobuf.message
+
 try:
     from google.api_core import client_logging  # type: ignore
     CLIENT_LOGGING_SUPPORTED = True  # pragma: NO COVER