def _nack(self, message_id, subscription_id, **kwargs):
        """Reject receipt of a message. This only makes sense when the
        'acknowledgement' flag was set for the relevant subscription.
        :param message_id: ID of the message to be rejected
        :param subscription: ID of the relevant subscriptiong
        :param **kwargs: Further parameters for the transport layer. For example
               transaction: Transaction ID if rejection should be part of a
                            transaction
        """
        self._conn.nack(message_id, subscription_id, **kwargs)