Flutter firestore append another QuerySnapshot

Question

how do I append another QuerySnapshot to a QuerySnapshot?

static final CollectionReference _col = FirebaseFirestore.instance.collection('post');
            
    Stream<QuerySnapshot<Object?>> query = _col.where('firstReleaseDate', isLessThanOrEqualTo: Timestamp.now()).snapshots();
            
        
        QuerySnapshot ss = await _col
          .query() <-----append here
          .orderBy(field, descending: isDescending)
          .startAfterDocument(lastDoc)
          .limit(limit)
          .get()
          .timeout(TIMEOUT_DURATION);