debounce<T>  static method 
Implementation
static ZenWorkerHandle debounce<T>(
  ValueNotifier<T> obs,
  void Function(T) callback,
  Duration duration,
) {
  if (duration.isNegative) {
    throw ArgumentError('Duration cannot be negative');
  }
  return watch<T>(obs, callback,
      type: WorkerType.debounce, duration: duration);
}