How does Query.prototype.hint() work in Mongoose ?

const mongoose = require('mongoose');

// Database connection
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', {
    useNewUrlParser: true,
    useCreateIndex: true,
    useUnifiedTopology: true
});

// User model
const User = mongoose.model('User', { 
    name: { type: String },
    age: { type: Number }
});

var query = User.find();
query.hint({index:1})

console.log("Hint:", query.options)

const express = require('express');
const mongoose = require('mongoose');
const app = express()

// Database connection
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', {
    useNewUrlParser: true,
    useCreateIndex: true,
    useUnifiedTopology: true
});

// User model
const User = mongoose.model('User', { 
    name: { type: String },
    age: { type: Number }
});

var query = User.find();
query.hint({index: -1})

console.log("Hint:", query.options)

app.listen(3000, function(error ) {
    if(error) console.log(error)
    console.log("Server listening on PORT 3000")
});