toJson method

Implementation

Map toJson(){
  Map result = {};

  if (face != null) result.addAll({"face": face});
  if (image != null) result.addAll({"image": image});
  if (faceIndex != null) result.addAll({"faceIndex": faceIndex});
  if (imageIndex != null) result.addAll({"imageIndex": imageIndex});

  return result;
}