如何让Firestore事务返回一个promise？

// 导入Firestore模块
const admin = require('firebase-admin');

// 创建Firestore实例
const db = admin.firestore();

// 定义事务函数
const transactionFunction = (transaction) => {
  const docRef = db.collection('myCollection').doc('myDocument');

  return transaction.get(docRef)
    .then((doc) => {
      if (!doc.exists) {
        throw new Error('Document does not exist!');
      }

      const data = doc.data();
      const newValue = data.value + 1;

      transaction.update(docRef, { value: newValue });
    });
};

// 执行事务并返回Promise
const transactionPromise = db.runTransaction(transactionFunction);

// 处理事务结果
transactionPromise.then(() => {
  console.log('Transaction completed successfully!');
}).catch((error) => {
  console.log('Transaction failed: ', error);
});