Cannot attach spy on the same function more than once about chai-spies HOT 2 CLOSED

const chai = require('chai');
const spies = require('chai-spies');
const { EventEmitter } = require('events');
chai.use(spies);

const emitter = new EventEmitter();

function foo() {
    const spy = chai.spy.on(emitter, 'emit');
};

function bar() {
    const spy = chai.spy.on(emitter, 'emit');
}

foo(); // OK
chai.spy.restore() // <-----
bar(); // Error: "emit" is already a spy