code: def _AddSerializePartialToStringMethod(message_descriptor, cls):
    
  
    def SerializePartialToString(self):
      out = BytesIO()
      self._InternalSerialize(out.write)
      return out.getvalue()
    cls.SerializePartialToString = SerializePartialToString
  
    def InternalSerialize(self, write_bytes):
      for field_descriptor, field_value in self.ListFields():
        field_descriptor._encoder(write_bytes, field_value)
      for tag_bytes, value_bytes in self._unknown_fields:
        write_bytes(tag_bytes)
        write_bytes(value_bytes)
    cls._InternalSerialize = InternalSerialize
docs: Helper for _AddMessageMethods().