sequence.go
func (s *FileSequence) PaddingStyle() PadStyle {
	for style, mapper := range padders {
		if mapper == s.padMapper {
			return style
		}
	}
	return PadStyleDefault
}
func (s *FileSequence) PaddingStyle() PadStyle {
	for style, mapper := range padders {
		if mapper == s.padMapper {
			return style
		}
	}
	return PadStyleDefault
}
// PaddingStyle returns the style of padding being used
// to convert between characters and their numeric width,
// i.e. # == 4