How to use the neo.Network.NodeLeader.NodeLeader.Instance function in neo

def test_initialize(self):
        leader = NodeLeader.Instance()
        self.assertEqual(leader.Peers, [])
        self.assertEqual(leader.KNOWN_ADDRS, [])

# Instantiate the blockchain and subscribe to notifications
    blockchain = LevelDBBlockchain(settings.chain_leveldb_path)
    Blockchain.RegisterBlockchain(blockchain)

    # Try to set up a notification db
    if NotificationDB.instance():
        NotificationDB.instance().start()

    # Start the prompt interface
    fn_prompt_history = os.path.join(settings.DATA_DIR_PATH, '.prompt.py.history')
    cli = PromptInterface(fn_prompt_history)

    # Run things
#    reactor.suggestThreadPoolSize(15)
    reactor.callInThread(cli.run)
    NodeLeader.Instance().Start()

    # reactor.run() is blocking, until `quit()` is called which stops the reactor.
    reactor.run()

    # After the reactor is stopped, gracefully shutdown the database.
    NotificationDB.close()
    Blockchain.Default().Dispose()
    NodeLeader.Instance().Shutdown()

args = parser.parse_args()

    if os.path.isfile(args.output):
        print("Error: Wallet file %s already exists" % args.output)
        exit(1)

    settings.setup_privnet()
    print("Blockchain DB path:", settings.chain_leveldb_path)
    if os.path.exists(settings.chain_leveldb_path):
        print("Warning: Chain database already exists. If this is from a previous private network, you need to delete %s" % settings.chain_leveldb_path)

    blockchain = LevelDBBlockchain(settings.chain_leveldb_path)
    Blockchain.RegisterBlockchain(blockchain)

    reactor.suggestThreadPoolSize(15)
    NodeLeader.Instance().Start()

    pc = PrivnetClaimall(args.output, args.password, args.time, args.save_privnet_wif)
    reactor.callInThread(pc.run)
    reactor.run()

def show_nodes(self):
        if len(NodeLeader.Instance().Peers) > 0:
            out = ""
            for peer in NodeLeader.Instance().Peers:
                out += "Peer %s - IO: %s\n" % (peer.Name(), peer.IOStats())
            print_tokens([(Token.Number, out)], self.token_style)
        else:
            print("Not connected yet\n")

# Instantiate the blockchain and subscribe to notifications
    blockchain = LevelDBBlockchain(settings.LEVELDB_PATH)
    Blockchain.RegisterBlockchain(blockchain)
    
    # Try to set up a notification db
    if NotificationDB.instance():
        NotificationDB.instance().start()

    cli = TheConstructInterface(input_args=args, debug=args.debug)
    

    # Run
    reactor.suggestThreadPoolSize(15)
    reactor.callInThread(cli.run)
    NodeLeader.Instance().Start()
    reactor.run()

return None

        wallet.Sign(context)

        if context.Completed:

            print("Signature complete, relaying...")

            tx = context.Verifiable
            tx.scripts = context.GetScripts()

            wallet.SaveTransaction(tx)

            print("will send tx: %s " % json.dumps(tx.ToJson(), indent=4))

            relayed = NodeLeader.Instance().Relay(tx)

            if relayed:
                print("Relayed Tx: %s " % tx.Hash.ToString())
                foundtx = self.wait_for_tx(tx)
                if foundtx:
                    print("Transaction found, all is good!")
                else:
                    print("Transaction NOT found!")
                return('success')

            else:
                print("Could not relay tx %s " % tx.Hash.ToString())
                return('fail')
        else:
            print("Transaction signed, but the signature is still incomplete")
            return(json.dumps(context.ToJson(), separators=(',', ':')))

return None

        wallet.Sign(context)

        if context.Completed:

            print("Signature complete, relaying...")

            tx = context.Verifiable
            tx.scripts = context.GetScripts()

            wallet.SaveTransaction(tx)

            print("will send tx: %s " % json.dumps(tx.ToJson(), indent=4))

            relayed = NodeLeader.Instance().Relay(tx)

            if relayed:
                print("Relayed Tx: %s " % tx.Hash.ToString())
                foundtx = self.wait_for_tx(tx)
                if foundtx:
                    print("Transaction found, all is good!")
                else:
                    print("Transaction NOT found!")
                return('success')

            else:
                print("Could not relay tx %s " % tx.Hash.ToString())
                return('fail')
        else:
            print("Transaction signed, but the signature is still incomplete")
            return(json.dumps(context.ToJson(), separators=(',', ':')))

def wait_for_peers(self):
        while len(NodeLeader.Instance().Peers) == 0:
            self.logger.debug('waiting for NodeLeader peers')
            sleep(1)

settings.setup_privnet()

    # Instantiate the blockchain and subscribe to notifications
    blockchain = LevelDBBlockchain(settings.chain_leveldb_path)
    Blockchain.RegisterBlockchain(blockchain)
    dbloop = task.LoopingCall(Blockchain.Default().PersistBlocks)
    dbloop.start(.1)

    ndb = NotificationDB.instance()
    ndb.start()

    api_server = RestApi()

    # Run
    reactor.suggestThreadPoolSize(15)
    NodeLeader.Instance().Start()

    port = 8000
    logger.info("Starting rest-api server on port %s" % (port))
    api_server.app.run('0.0.0.0', port)