code: def nack(self, items):
          
          self.modify_ack_deadline(
              [requests.ModAckRequest(ack_id=item.ack_id, seconds=0) for item in items]
          )
          self.drop([requests.DropRequest(*item) for item in items])
docs: Explicitly deny receipt of messages.
  
          Args:
              items(Sequence[NackRequest]): The items to deny.