toHHMMSS method
Formats this duration as HH:MM:SS or MM:SS.
Implementation
String toHHMMSS() {
final h = inHours.abs();
final m = inMinutes.abs().remainder(60);
final s = inSeconds.abs().remainder(60);
final hh = h > 0 ? '${h.toString().padLeft(2, '0')}:' : '';
return '$hh${m.toString().padLeft(2, '0')}:${s.toString().padLeft(2, '0')}';
}