How to use the @angular/fire._firebaseAppFactory function in @angular/fire

this.functions = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.functions(region || undefined);
    });

this.storage = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.storage(storageBucket || undefined);
    });
  }

this.auth = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.auth();
    });

      map(() => _firebaseAppFactory(options, zone, nameOrConfig)),
      map(app => app.remoteConfig()),

this.database = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.database(databaseURL || undefined);
    });
  }

this.database = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.database(databaseURL || undefined);
    });
  }

      map(() => _firebaseAppFactory(options, zone, nameOrConfig)),
      map(app => app.messaging()),

      map(() => _firebaseAppFactory(options, zone, nameOrConfig)),
      map(app => app.analytics()),