Dart APIunself_modelArchiveFormattoJson toJson method Null safety Map<String, dynamic> toJson() inherited Implementation Map<String, dynamic> toJson() => throw _privateConstructorUsedError; unself_model unself_model ArchiveFormat toJson method ArchiveFormat class Constructors ArchiveFormat fromJson Properties app constraint copyWith created extra format hashCode id mappings runtimeType updated version Methods noSuchMethod toJson toString Operators operator ==