There were some manual (via `sed` with the command line) edits
made for certain gRPC related parts of `*_pb2.py` files that
used dispatch tables to map service names onto request/response
protobuf types. For example

  request_deserializers = {
    ('google.longrunning.Operations', 'CancelOperation'): google.longrunning.operations_pb2.CancelOperationRequest.FromString,
    ('google.longrunning.Operations', 'DeleteOperation'): google.longrunning.operations_pb2.DeleteOperationRequest.FromString,
    ('google.longrunning.Operations', 'GetOperation'): google.longrunning.operations_pb2.GetOperationRequest.FromString,
    ('google.longrunning.Operations', 'ListOperations'): google.longrunning.operations_pb2.ListOperationsRequest.FromString,
  }

needed to be transformed into

  request_deserializers = {
    ('google.longrunning.Operations', 'CancelOperation'): gcloud.bigtable._generated.operations_pb2.CancelOperationRequest.FromString,
    ('google.longrunning.Operations', 'DeleteOperation'): gcloud.bigtable._generated.operations_pb2.DeleteOperationRequest.FromString,
    ('google.longrunning.Operations', 'GetOperation'): gcloud.bigtable._generated.operations_pb2.GetOperationRequest.FromString,
    ('google.longrunning.Operations', 'ListOperations'): gcloud.bigtable._generated.operations_pb2.ListOperationsRequest.FromString,
  }