sequence.go
func (s *FileSequence) FrameRangePadded() string {
	if s.frameSet == nil {
		return ""
	}
	return s.frameSet.FrameRangePadded(s.zfill)
}
func (s *FileSequence) FrameRangePadded() string {
	if s.frameSet == nil {
		return ""
	}
	return s.frameSet.FrameRangePadded(s.zfill)
}
// FrameRangePadded returns the string frame range component,
// parsed from the sequence, and padded out by the pad characters.
// If no frame range was parsed, then this method will return an empty string.