sequence.go
func (s *FileSequence) String() string {
	var fs string
	if s.frameSet != nil {
		fs = s.frameSet.String()
	}
	buf := bytes.NewBufferString(s.dir)
	buf.WriteString(s.basename)
	buf.WriteString(fs)
	buf.WriteString(s.padChar)
	buf.WriteString(s.ext)
	return buf.String()
}
func (s *FileSequence) String() string {
	var fs string
	if s.frameSet != nil {
		fs = s.frameSet.String()
	}
	buf := bytes.NewBufferString(s.dir)
	buf.WriteString(s.basename)
	buf.WriteString(fs)
	buf.WriteString(s.padChar)
	buf.WriteString(s.ext)
	return buf.String()
}
// String returns the formatted sequence