code: def _send_rst(self, transaction):  # pragma: no cover
          
  
          rst = Message()
          rst.type = defines.Types['RST']
  
          if not transaction.response.acknowledged:
              rst = self._messageLayer.send_empty(transaction, transaction.response, rst)
              self.send_datagram(rst)
docs: Sends an RST message for the response.
  
          :param transaction: transaction that holds the response