hint method
Implementation
Future<void> hint({final Duration? duration, final Duration? total}) async {
assert(controller is AnimationController);
if (controller is! AnimationController) return;
if (controller!.isAnimating || controller!.value != 0) return;
final Duration? durationTotal = total ?? controller!.duration;
final Completer completer = Completer();
final Duration? original = controller!.duration;
controller!.duration = durationTotal;
await controller!.forward();
final Duration durationFlipBack = duration ?? const Duration(milliseconds: 150);
Timer(durationFlipBack, () {
controller!.reverse().whenComplete(completer.complete);
controller!.duration = original;
});
await completer.future;
}