How to use the backend-js.QueryExpression function in backend-js

/*jslint node: true */
/*jshint esversion: 6 */
/*global Symbol*/
'use strict';

let backend = require('backend-js');
let ModelEntity = backend.ModelEntity;
let QueryExpression = backend.QueryExpression;
let Sequelize = require('sequelize');
require('sequelize-values')(Sequelize);
let VariableAdaptor = require('sequelize-transparent-cache-variable');
let withCache = require('sequelize-transparent-cache')(new VariableAdaptor()).withCache;

let Op = Sequelize.Op;

var LogicalOperators = module.exports.LogicalOperators = {

    AND: Op.and,
    OR: Op.or,
    NOT: Op.not
};

var ComparisonOperators = module.exports.ComparisonOperators = {

/*jslint node: true */
/*jshint esversion: 6 */
/*global emit*/
/*global _*/
'use strict';

let backend = require('backend-js');
let ModelEntity = backend.ModelEntity;
let QueryExpression = backend.QueryExpression;
let AggregateExpression = backend.AggregateExpression;
let mongoose = require('mongoose');
mongoose.Promise = global.Promise;
let Schema = mongoose.Schema;
let autoIncrement = require('mongodb-autoincrement');
mongoose.plugin(autoIncrement.mongoosePlugin);
require('mongoose-pagination');
var cacheOpts = {

    max: 50,
    maxAge: 1000 * 60 * 2
};
require('mongoose-cache').install(mongoose, cacheOpts);

module.exports.LogicalOperators = {