Dart APIunself_modelArchiveDatatoJson toJson method Null safety Map<String, dynamic> toJson() inherited Implementation Map<String, dynamic> toJson() => throw _privateConstructorUsedError; unself_model unself_model ArchiveData toJson method ArchiveData class Constructors ArchiveData fromJson Properties accounts activities apps archiveId copyWith extra hashCode id runtimeType topics Methods noSuchMethod toJson toString Operators operator == Constants fieldMap