getting error : Cannot read property 'findOne' of undefined in node js - node.js

Question

i have created sample page, and when i run my page node airbnb-library.js i am getting error, Cannot read property 'findOne' of undefined can anyone please help me why i am getting this error ? here i have attached my code, can anyone please look my code and help me to resolve this issue ? any help will be really appreciated...
db.js
const config = require('../config.json');
const mysql = require('mysql2/promise');
const { Sequelize } = require('sequelize');
module.exports = db = {};
initialize();
async function initialize() {
// create db if it doesn't already exist
const { host, port, user, password, database } = config.database;
const connection = await mysql.createConnection({ host, port, user, password });
await connection.query(`CREATE DATABASE IF NOT EXISTS \`${database}\`;`);
// connect to db
const sequelize = new Sequelize(database, user, password, { host: host, port: port, dialect: 'mysql' });
// init models and add them to the exported db object
db.User = require('../users/user.model')(sequelize);
db.Airbnb = require('../users/airbnb.model')(sequelize);
// sync all models with database
await sequelize.sync();
}
airbnb-library.js
const http = require("http");
const requestapi = require('request');
const airbnb = require('airbnbapijs')
async function test() {
const airbnbdata = await airbnb.newAccessToken({ username: 'dino#pushideas.com', password: 'Christmas2016!'})
console.log(airbnbdata);
}
let airbnbdata = test();
main.js
const config = require('../../../config.json');
const airbnb = require('airbnbapijs')
const requestapi = require('request');
const http = require("http");
async newAccessToken({ username, password } = {}) {
try {
await this.airbnblogin({"email":username,"password":password});
} catch (e) {
console.log(e);
}
}
async airbnblogin(params) {
let account = await db.Airbnb.findOne({ where: { airbnb_email: params.email, } })
}