Dart APIunself_modelUnionUnion.fromJson factory constructor Union.fromJson constructor Null safety Union.fromJson(Map<String, dynamic> json ) Implementation factory Union.fromJson(Map<String, dynamic> json) = _$Union.fromJson; unself_model unself_model Union Union.fromJson factory constructor Union class Constructors Union fromJson Properties copyWith hashCode key names runtimeType Methods getScheme map mapOrNull maybeMap maybeWhen noSuchMethod toJson toString useId when whenOrNull Operators operator ==