toJson method Null safety

Implementation

Map<String, dynamic> toJson() {
  final json = <String, dynamic>{};
  json.addAll({
    'isImport': isImport,
    'isDeferred': isDeferred,
    'prefix': prefix,
    'target': target?.toJson(),
  });
  _setIfNotNull(json, 'shows', shows?.map((f) => f).toList());
  _setIfNotNull(json, 'hides', hides?.map((f) => f).toList());
  return json;
}