code: def do_execute(self):
          
          conv = self.config["setup"].shallow_copy()
          conv.input = self._input.payload
          result = conv.convert()
          if result is None:
              if conv.output is not None:
                  self._output.append(Token(conv.output))
          return None
docs: The actual execution of the actor.
  
          :return: None if successful, otherwise error message
          :rtype: str