Dart APIunself_modelActivityappId appId property Null safety String appId inherited appId is the source node. Implementation String get appId => throw _privateConstructorUsedError; unself_model unself_model Activity appId property Activity class Constructors Activity fromJson Properties accountId appId archiveId copyWith created extra hashCode id labels name runtimeType source sourceId targetId timestamp type updated Methods noSuchMethod toJson toString Operators operator ==