code: def consume(self, callback, queue):
          
          if queue in self._consumers and self._consumers[queue].channel.is_open:
              consumer = Consumer(
                  tag=self._consumers[queue].tag,
                  queue=queue,
                  callback=callback,
                  channel=self._consumers[queue].channel,
              )
              self._consumers[queue] = consumer
              defer.returnValue(consumer)
  
          channel = yield self._allocate_channel()
          consumer = Consumer(
              tag=str(uuid.uuid4()), queue=queue, callback=callback, channel=channel
          )
  
          self._consumers[queue] = consumer
          if not self._running:
              yield self.resumeProducing()
              defer.returnValue(consumer)
  
          queue_object, _ = yield consumer.channel.basic_consume(
              queue=consumer.queue, consumer_tag=consumer.tag
          )
          deferred = self._read(queue_object, consumer)
          deferred.addErrback(
              lambda f: _legacy_twisted_log.msg,
              "_read failed on consumer {c}",
              c=consumer,
              logLevel=logging.ERROR,
          )
          _legacy_twisted_log.msg("Successfully registered AMQP consumer {c}", c=consumer)
          defer.returnValue(consumer)
docs: Register a message consumer that executes the provided callback when
          messages are received.
  
          The queue must exist prior to calling this method.  If a consumer
          already exists for the given queue, the callback is simply updated and
          any new messages for that consumer use the new callback.
  
          If :meth:`resumeProducing` has not been called when this method is called,
          it will be called for you.
  
          Args:
              callback (callable): The callback to invoke when a message is received.
              queue (str): The name of the queue to consume from.
  
          Returns:
              fedora_messaging.twisted.protocol.Consumer: A namedtuple that
              identifies this consumer.
  
          NoFreeChannels: If there are no available channels on this connection.
              If this occurs, you can either reduce the number of consumers on this
              connection or create an additional connection.