code: def do_execute(self):
          
          if isinstance(self.input.payload, classes.JavaObject) and self.input.payload.is_serializable:
              copy = serialization.deepcopy(self.input.payload)
              if copy is not None:
                  self._output.append(Token(copy))
          else:
              self._output.append(self.input)
          return None
docs: The actual execution of the actor.
  
          :return: None if successful, otherwise error message
          :rtype: str