code: def CopyToProto(self, proto):
      
      if (self.file is not None and
          self._serialized_start is not None and
          self._serialized_end is not None):
        proto.ParseFromString(self.file.serialized_pb[
            self._serialized_start:self._serialized_end])
      else:
        raise Error('Descriptor does not contain serialization.')
docs: Copies this to the matching proto in descriptor_pb2.
  
      Args:
        proto: An empty proto instance from descriptor_pb2.
  
      Raises:
        Error: If self couldnt be serialized, due to to few constructor arguments.