import { AngularFirestore } from '@angular/fire/firestore';import { Observable } from 'rxjs';// Replace `userId` with the actual user ID you want to retrieve the list of products forconst userId = 'user123';export class ProductService {  constructor(private firestore: AngularFirestore) {}  getProductsForUser(): Observable<any> {    return this.firestore      .collection('users')      .doc(userId)      .collection('products')      .valueChanges();  }}