Trying to list collection of Firestore Database

I’d like to list of the collection of Firestore database inside Ionic4 app so I use the doc in the section listCollection so I applied the example code in my code :

this.afs.firestore.listCollections().then(collections => {
  for (let collection of collections) {
    console.log(`Found collection with id: ${collection.id}`);
  }
});

here is my constructor :

  constructor(private router: Router,
              private afs: AngularFirestore,
              private fireauth: AngularFireAuth) { }

And I get this error : error TS2339: Property ‘listCollections’ does not exist on type ‘Firestore’.

I can not use the property listCollections whereas it is in the online doc…

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Source Url Trying to list collection of Firestore Database