code: def requeue(self):
          
          if self.acknowledged:
              raise self.MessageStateError(
                  "Message already acknowledged with state: %s" % self._state)
          self.backend.requeue(self.delivery_tag)
          self._state = "REQUEUED"
docs: Reject this message and put it back on the queue.
  
          You must not use this method as a means of selecting messages
          to process.
  
          :raises MessageStateError: If the message has already been
              acknowledged/requeued/rejected.