在Cloud Function中，什么语法用于写入Firestore子集合？

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.createSubcollection = functions.https.onRequest(async (req, res) => {
  try {
    const parentDocId = req.query.parentDocId; // 获取父文档的ID
    const subcollectionName = req.query.subcollectionName; // 子集合的名称

    // 创建子集合的引用
    const parentDocRef = admin.firestore().collection('parentCollection').doc(parentDocId);
    const subcollectionRef = parentDocRef.collection(subcollectionName);

    // 向子集合中添加文档
    await subcollectionRef.add({ 
      // 添加的文档数据
      field1: 'value1',
      field2: 'value2',
    });

    res.status(200).send('Subcollection created successfully');
  } catch (error) {
    console.error('Error creating subcollection:', error);
    res.status(500).send('Error creating subcollection');
  }
});