Dart APIunself_modelCollectiontoJson toJson method Null safety Map<String, dynamic> toJson() inherited Implementation Map<String, dynamic> toJson() => throw _privateConstructorUsedError; unself_model unself_model Collection toJson method Collection class Constructors Collection fromJson Properties copyWith created createRule deleteRule extra hashCode id listRule name runtimeType system type updated updateRule viewRule Methods noSuchMethod toJson toString Operators operator ==