sortPOIsByGraphDistance method
sort all POIs by Graph distance from user location
Implementation
Future<List<PointOfInterestWithInfo>> sortPOIsByGraphDistance() async {
  List<dynamic> poisWithInfoList = await _channel.invokeMethod('sortPOIsByGraphDistance');
  return poisWithInfoList
      .map((poiWithInfoMap) => PointOfInterestWithInfo.fromMap(poiWithInfoMap))
      .toList();
}