durationFormatter method
Implementation
@override
String durationFormatter(Duration duration) {
final int hours = duration.inHours;
final String formatter =
[if (hours != 0) hours, duration.inMinutes, duration.inSeconds].map((seg) => seg.abs().remainder(60).toString().padLeft(2, '0')).join(':');
return duration.inSeconds < 0 ? "-$formatter" : formatter;
}