frameset.go
func (s *FrameSet) InvertedFrameRange(pad int) string {
	frange := s.rangePtr.Inverted().String()
	if pad > 1 {
		frange = PadFrameRange(frange, pad)
	}
	return frange
}
func (s *FrameSet) InvertedFrameRange(pad int) string {
	frange := s.rangePtr.Inverted().String()
	if pad > 1 {
		frange = PadFrameRange(frange, pad)
	}
	return frange
}
// InvertedFrameRange returns a new frame range string that represents
// all frames *not* within the current FrameSet. That is, it
// will create a range that "fills in" the current one.