如何复制具有新日期的旧文档(flutter firestore)？

dependencies:
  cloud_firestore: ^2.5.4

import 'package:cloud_firestore/cloud_firestore.dart';

final CollectionReference documentsCollection = FirebaseFirestore.instance.collection('documents');
final DocumentReference oldDocumentRef = documentsCollection.doc('old_document_id');

final DocumentSnapshot oldDocumentSnapshot = await oldDocumentRef.get();
final Map<String, dynamic> oldData = oldDocumentSnapshot.data() as Map<String, dynamic>;

final DocumentReference newDocumentRef = documentsCollection.doc('new_document_id');
final Map<String, dynamic> newData = Map<String, dynamic>.from(oldData);
newData['date'] = DateTime.now(); // 更新日期字段为当前日期

await newDocumentRef.set(newData);