encode method Null safety

Implementation

Object encode() {
  final Map<Object?, Object?> pigeonMap = <Object?, Object?>{};
  pigeonMap['styleURL'] = styleURL;
  pigeonMap['geometry'] = geometry;
  pigeonMap['minZoom'] = minZoom;
  pigeonMap['maxZoom'] = maxZoom;
  pigeonMap['pixelRatio'] = pixelRatio;
  pigeonMap['glyphsRasterizationMode'] = glyphsRasterizationMode.index;
  return pigeonMap;
}