allPolygons method
Implementation
List<Polygon> allPolygons() {
List<Polygon> polygons = [];
polygons.addAll(this.polygons.sublist(0));
if (front != null) polygons = List.from(polygons)..addAll(front!.allPolygons());
if (back != null) polygons = List.from(polygons)..addAll(back!.allPolygons());
return polygons;
}