How to use the pysyncobj.config.FAIL_REASON function in pysyncobj

def _applyCommand(self, command, callback, commandType = None):
        try:
            if commandType is None:
                self.__commandsQueue.put_nowait((command, callback))
            else:
                self.__commandsQueue.put_nowait((_bchr(commandType) + command, callback))
            if not self.__conf.appendEntriesUseBatch and PIPE_NOTIFIER_ENABLED:
                self.__pipeNotifier.notify()
        except Queue.Full:
            self.__callErrCallback(FAIL_REASON.QUEUE_FULL, callback)

'request_id': requestID,
                            'log_idx': idx,
                            'log_term': term,
                        })
                    if not self.__conf.appendEntriesUseBatch:
                        self.__sendAppendEntries()
                else:

                    if requestNode is None:
                        if callback is not None:
                            callback(None, FAIL_REASON.REQUEST_DENIED)
                    else:
                        self.__transport.send(requestNode, {
                            'type': 'apply_command_response',
                            'request_id': requestID,
                            'error': FAIL_REASON.REQUEST_DENIED,
                        })

            elif self.__raftLeader is not None:
                if requestNode is None:
                    message = {
                        'type': 'apply_command',
                        'command': command,
                    }

                    if callback is not None:
                        self.__commandsLocalCounter += 1
                        self.__commandsWaitingReply[self.__commandsLocalCounter] = callback
                        message['request_id'] = self.__commandsLocalCounter

                    self.__transport.send(self.__raftLeader, message)
                else:

needSendAppendEntries = False

        if self.__raftCommitIndex > self.__raftLastApplied:
            count = self.__raftCommitIndex - self.__raftLastApplied
            entries = self.__getEntries(self.__raftLastApplied + 1, count)
            for entry in entries:
                try:
                    currentTermID = entry[2]
                    subscribers = self.__commandsWaitingCommit.pop(entry[1], [])
                    res = self.__doApplyCommand(entry[0])
                    for subscribeTermID, callback in subscribers:
                        if subscribeTermID == currentTermID:
                            callback(res, FAIL_REASON.SUCCESS)
                        else:
                            callback(None, FAIL_REASON.DISCARDED)

                    self.__raftLastApplied += 1
                except SyncObjExceptionWrongVer as e:
                    logging.error('request to switch to unsupported code version (self version: %d, requested version: %d)' %
                        (self.__selfCodeVersion, e.ver))


            if not self.__conf.appendEntriesUseBatch:
                needSendAppendEntries = True

        if self.__raftState == _RAFT_STATE.LEADER:
            if time.time() > self.__newAppendEntriesTime or needSendAppendEntries:
                self.__sendAppendEntries()

        if not self.__onReadyCalled and self.__raftLastApplied == self.__leaderCommitIndex:
            if self.__conf.onReady:

self.__setState(_RAFT_STATE.FOLLOWER)
                self.__raftLeader = None

        needSendAppendEntries = False

        if self.__raftCommitIndex > self.__raftLastApplied:
            count = self.__raftCommitIndex - self.__raftLastApplied
            entries = self.__getEntries(self.__raftLastApplied + 1, count)
            for entry in entries:
                try:
                    currentTermID = entry[2]
                    subscribers = self.__commandsWaitingCommit.pop(entry[1], [])
                    res = self.__doApplyCommand(entry[0])
                    for subscribeTermID, callback in subscribers:
                        if subscribeTermID == currentTermID:
                            callback(res, FAIL_REASON.SUCCESS)
                        else:
                            callback(None, FAIL_REASON.DISCARDED)

                    self.__raftLastApplied += 1
                except SyncObjExceptionWrongVer as e:
                    logging.error('request to switch to unsupported code version (self version: %d, requested version: %d)' %
                        (self.__selfCodeVersion, e.ver))


            if not self.__conf.appendEntriesUseBatch:
                needSendAppendEntries = True

        if self.__raftState == _RAFT_STATE.LEADER:
            if time.time() > self.__newAppendEntriesTime or needSendAppendEntries:
                self.__sendAppendEntries()

def __onLeaderChanged(self):
        for id in sorted(self.__commandsWaitingReply):
            self.__commandsWaitingReply[id](None, FAIL_REASON.LEADER_CHANGED)
        self.__commandsWaitingReply = {}

message = {
                        'type': 'apply_command',
                        'command': command,
                    }

                    if callback is not None:
                        self.__commandsLocalCounter += 1
                        self.__commandsWaitingReply[self.__commandsLocalCounter] = callback
                        message['request_id'] = self.__commandsLocalCounter

                    self.__transport.send(self.__raftLeader, message)
                else:
                    self.__transport.send(requestNode, {
                        'type': 'apply_command_response',
                        'request_id': requestID,
                        'error': FAIL_REASON.NOT_LEADER,
                    })
            else:
                self.__callErrCallback(FAIL_REASON.MISSING_LEADER, callback)

}

                    if callback is not None:
                        self.__commandsLocalCounter += 1
                        self.__commandsWaitingReply[self.__commandsLocalCounter] = callback
                        message['request_id'] = self.__commandsLocalCounter

                    self.__transport.send(self.__raftLeader, message)
                else:
                    self.__transport.send(requestNode, {
                        'type': 'apply_command_response',
                        'request_id': requestID,
                        'error': FAIL_REASON.NOT_LEADER,
                    })
            else:
                self.__callErrCallback(FAIL_REASON.MISSING_LEADER, callback)