我希望子集合中的调用数据包含我突出显示的特定数据

export class FirebaseService {

    onsiteRef: AngularFirestoreCollectionGroup<Onsiteinterface>;

    constructor(private db: AngularFirestore, public ngFireAuth: 
    AngularFireAuth)  { 
        this.onsiteRef = db.collectionGroup('Request', ref => 
        ref.where('Onsite','==','Onsite'));
    }