此函数仅从firebase添加一条记录，但根据我的条件，它应添加条件为真的所有记录
功能：

final Set<Marker> _markers = <Marker>{}; //My marker List

Future<void> markSetss() async {
QuerySnapshot querySnapshot = await FirebaseFirestore.instance
    .collection('stations')
    .where('norequest', isGreaterThanOrEqualTo: 5)
    .get();

List<Map<String?, dynamic>> results = querySnapshot.docs
    .map((doc) => {
          _markers.add(
            Marker(
              markerId: MarkerId(doc['norequest'].toString()),
              position: LatLng(doc['coor'].latitude, doc['coor'].longitude),
            ),
          ),
        } as Map<String, dynamic>)
    .toList();
}

Firebase记录：第一次