I am building a screen in flutter where by selecting the city we can see the administrative area of the city using thepolyline. I am using open maps api for that . This is working fine in case of polygon . but the issue is when the city is getting multipolygon in the result the model conversion is not working or to be honest I am not capable of it to convert it. I am attaching all the nmultipolygon data using pastebin as that's a large file GeoJson Multi Polygon Data

Now I am attaching my class where I am converting it from the json

    class Geojson {
  final String? type;
  final List<XPolygon> coordinates;
  final List<List> polyCoordinates;

  Geojson({
    this.type,
    this.coordinates = const [],
    this.polyCoordinates = const [],
  });

  factory Geojson.fromJson(Map<String, dynamic> json) => Geojson(
      type: json["type"],
      coordinates: json["type"] != "Polygon"
          ? []
          : json["coordinates"] == null
              ? []
              : (json["coordinates"] as List).isEmpty
                  ? []
                  : (json["coordinates"] as List)
                      .expand((polygonData) => polygonData)
                      .map((e) => XPolygon(
                          lat: e.last.toString(), long: e.first.toString()))
                      .toList(),
      polyCoordinates: json["type"] != "MultiPolygon"
          ? []
          : (json["coordinates"] as List<List>)
              .expand((polygonData) => polygonData)
              .map(
                (e) => e
                    .map(
                      (e) => XPolygon(
                          lat: e.last.toString(), long: e.first.toString()),
                    )
                    .toList(),
              )
              .toList()
      // : [
      //     ...[json["coordinates"][0]]
      //   ]
      //     .map((e) => XPolygon(
      //         lat: e.last.toString(), long: e.first.toString()))
      //     .toList(),
      );

  Map<String, dynamic> toJson() => {
        "type": type,
        "coordinates": coordinates,
        "polyCoordinates": polyCoordinates
      };

  @override
  String toString() => jsonEncode(toJson());
}

Now I am attaching the logic where I am using the list to display the polylines in ui

     List<LatLng> cityboundaryCoordinates = [];
  List<List<LatLng>> multiPolyCityBounderyCoordinates = [];
  createCityPolyLine() {
    if (cityboundaryCoordinates.length > 3) {
      polylines.add(
        Polyline(
          polylineId: PolylineId(cityboundaryCoordinates.first.toString()),
          points: cityboundaryCoordinates,
          width: 3,
          color: Colors.red,
        ),
      );
    }
    if (multiPolyCityBounderyCoordinates.length > 3) {}
  }

for polygos the screen is displaying polylines of the city. For multipolygon what I need to do to make it work?? Please if possible specify the changes so that it will be easy for me to do the changes. Thanks for noticing it.