code: def _StubMethod(self, stub, method_descriptor,
                    rpc_controller, request, callback):
      
      return stub.rpc_channel.CallMethod(
          method_descriptor, rpc_controller, request,
          method_descriptor.output_type._concrete_class, callback)
docs: The body of all service methods in the generated stub class.
  
      Args:
        stub: Stub instance.
        method_descriptor: Descriptor of the invoked method.
        rpc_controller: Rpc controller to execute the method.
        request: Request protocol message.
        callback: A callback to execute when the method finishes.
      Returns:
        Response message (in case of blocking call).