code: def _GetResponseClass(self, method_descriptor):
      
      if method_descriptor.containing_service != self.descriptor:
        raise RuntimeError(
            'GetResponseClass() given method descriptor for wrong service type.')
      return method_descriptor.output_type._concrete_class
docs: Returns the class of the response protocol message.
  
      Args:
        method_descriptor: Descriptor of the method for which to return the
          response protocol message class.
  
      Returns:
        A class that represents the output protocol message of the specified
        method.