def _on_cancelok(self, cancel_frame):
        """
        Called when the server acknowledges a cancel request.

        Args:
            cancel_frame (pika.spec.Basic.CancelOk): The cancelok frame from
                the server.
        """
        _log.info("Consumer canceled; returning all unprocessed messages to the queue")
        self._channel.basic_nack(delivery_tag=0, multiple=True, requeue=True)