Getting db.close is not a function in sample JEST

I'm trying to setup testing my node with mongo app using Jest. I've set it up and copied their sample verbatim, which works fine, except when I call the db.close(); function. It gives me a TypeError: that db.close is not a function. This is directly out of their example:

import { MongoClient } from 'mongodb';

describe('insert', () => {
    let connection;
    let db;
  
    beforeAll(async () => {
      connection = await MongoClient.connect(global.__MONGO_URI__, {
        useNewUrlParser: true,
      });
      db = await connection.db(global.__MONGO_DB_NAME__);
    });
  
    afterAll(async () => {
      await connection.close();
      await db.close();
    });
  
    it('should insert a doc into collection', async () => {
      const users = db.collection('users');
  
      const mockUser = {_id: 'some-user-id', name: 'John'};
      await users.insertOne(mockUser);
  
      const insertedUser = await users.findOne({_id: 'some-user-id'});
      expect(insertedUser).toEqual(mockUser);
    });
  });