Dart APIunself_modelJsonRefValuetoJson toJson method Null safety Map<String, dynamic> toJson() inherited Implementation Map<String, dynamic> toJson() => throw _privateConstructorUsedError; unself_model unself_model JsonRefValue toJson method JsonRefValue class Constructors fromJson slugFrom valueFrom Properties copyWith hashCode name runtimeType Methods map mapOrNull maybeMap maybeWhen noSuchMethod toJson toString when whenOrNull Operators operator ==