code: def ack(self):
          
          if self.acknowledged:
              raise self.MessageStateError(
                  "Message already acknowledged with state: %s" % self._state)
          self.backend.ack(self.delivery_tag)
          self._state = "ACK"
docs: Acknowledge this message as being processed.,
          This will remove the message from the queue.
  
          :raises MessageStateError: If the message has already been
              acknowledged/requeued/rejected.