Dart APIunself_modelJsonSchematoJson toJson method Null safety Map<String, dynamic> toJson() inherited Implementation Map<String, dynamic> toJson() => throw _privateConstructorUsedError; unself_model unself_model JsonSchema toJson method JsonSchema class Constructors entity flat fromJson struct Properties copyWith definition extra hashCode name runtimeType Methods map mapOrNull maybeMap maybeWhen noSuchMethod toJson toString when whenOrNull Operators operator ==