angular firestore中有.get()吗？

import { AngularFirestore, AngularFirestoreCollection } from '@angular/fire/firestore';
import { Observable } from 'rxjs';

// 在构造函数中注入AngularFirestore
constructor(private firestore: AngularFirestore) {}

// 获取集合中的所有文档
getDocuments(collectionName: string): Observable<any[]> {
  const collection: AngularFirestoreCollection<any> = this.firestore.collection(collectionName);
  return collection.get().pipe(
    map((querySnapshot) => {
      const documents: any[] = [];
      querySnapshot.forEach((doc) => {
        documents.push(doc.data());
      });
      return documents;
    })
  );
}

// 获取特定文档的数据
getDocument(collectionName: string, documentId: string): Observable<any> {
  const document = this.firestore.collection(collectionName).doc(documentId);
  return document.get().pipe(
    map((doc) => {
      if (doc.exists) {
        return doc.data();
      } else {
        return null;
      }
    })
  );
}