如何使用flutter从firestore中获取子集？

import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

final FirebaseFirestore firestore = FirebaseFirestore.instance;

QuerySnapshot querySnapshot = await firestore
    .collection('your_collection_path')
    .where('your_field', isEqualTo: 'your_value')
    .get();

if (querySnapshot.docs.isNotEmpty) {
  // 子集数据存在
  List<DocumentSnapshot> documents = querySnapshot.docs;
  for (DocumentSnapshot document in documents) {
    // 处理每个子集数据
    Map<String, dynamic> data = document.data();
    // 进行你的业务逻辑操作
  }
} else {
  // 子集数据不存在
}