toJson method

Implementation

Map toJson(){
  Map result = {};

  if (first != null) result.addAll({"first": first});
  if (second != null) result.addAll({"second": second});
  if (similarity != null) result.addAll({"similarity": similarity});
  if (score != null) result.addAll({"score": score});
  if (exception != null) result.addAll({"exception": exception});

  return result;
}