code: def reject(self):
          
          if self.acknowledged:
              raise self.MessageStateError(
                  "Message already acknowledged with state: %s" % self._state)
          self.backend.reject(self.delivery_tag)
          self._state = "REJECTED"
docs: Reject this message.
  
          The message will be discarded by the server.
  
          :raises MessageStateError: If the message has already been
              acknowledged/requeued/rejected.