Explicitly deny receipt of messages.

        Args:
            items(Sequence[NackRequest]): The items to deny.

def nack(self, items):
        """Explicitly deny receipt of messages.

        Args:
            items(Sequence[NackRequest]): The items to deny.
        """
        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])