build method
Subclasses should override this function to actually call the appropriate
build function (e.g., StatelessWidget.build or State.build) for
their widget.
Implementation
@override
Widget build() {
  if (_dirty) {
    notifyClients(widget);
  }
  // return Notifier.instance.notifyAppend(
  //   NotifyData(
  //       disposers: disposers, updater: getUpdate, throwException: false),
  return super.build();
  //);
}