Getting error- Advanced Node and Express - Implement the Serialization of a User Object

Please help me with this !!

:

My server.js code:
‘use strict’;

const express = require(‘express’);
const bodyParser = require(‘body-parser’);
const fccTesting = require(’./freeCodeCamp/fcctesting.js’);
const session = require(‘express-session’);
const passport = require(‘passport’);
const ObjectID = require(‘mongodb’).ObjectID;
const mongo = require(‘mongodb’).MongoClient;

const app = express();
app.set(‘view engine’,‘pug’);

fccTesting(app); //For FCC testing purposes
app.use(’/public’, express.static(process.cwd() + ‘/public’));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

app.use(session({
secret: process.env.SESSION_SECRET,
resave: true,
saveUninitialized: true,
}));
app.use(passport.initialize());
app.use(passport.session());

/app.route(’/’)
.get((req, res) => {
res.sendFile(process.cwd() + ‘/views/pug/index.pug’);
});
/

mongo.connect(process.env.DATABASE, (err, db) => {
if(err) {
console.log('Database error: ’ + err);
} else {
console.log(‘Successful database connection’);

   passport.serializeUser((user, done) => {

done(null, user._id);
});
passport.deserializeUser((id, done) => {
db.collection(‘users’).findOne(
{_id: new ObjectID(id)},
(err, doc) => {
done(null, doc);
}
);
});

app.route(’/’).get((req, res) => res.render(
process.cwd() + ‘/views/pug/index.pug’,
{
title: ‘Hello’,
message: ‘Please login’,
showLogin: true,
showRegistration: true
}
));

app.listen(process.env.PORT || 3000, () => {
console.log("Listening on port " + process.env.PORT);
});
}
});

Advanced node and express:Serialization of a user object

Link to the challenge: