fromIterable function
Implementation
TimerGenerator fromIterable(Iterable<DateTime> iterable) {
  final iterator = iterable.iterator;
  return (DateTime? now) {
    return iterator.moveNext() ? iterator.current : null;
  };
}
TimerGenerator fromIterable(Iterable<DateTime> iterable) {
  final iterator = iterable.iterator;
  return (DateTime? now) {
    return iterator.moveNext() ? iterator.current : null;
  };
}