debounce<T>  method 
Implementation
ZenWorkerHandle debounce<T>(
  ValueNotifier<T> obs,
  void Function(T) callback,
  Duration duration,
) {
  if (duration.isNegative || duration == Duration.zero) {
    throw ArgumentError('Debounce duration must be positive');
  }
  return _createWorker(
      () => ZenWorkers.debounce<T>(obs, callback, duration), 'debounce');
}