func FileSequence_Format(id FileSeqId, tpl *C.char) (*C.char, Error) {
	fs, ok := sFileSeqs.Get(id)
	if !ok {
		return C.CString(""), nil
	}

	str, err := fs.Format(C.GoString(tpl))
	if err != nil {
		return nil, C.CString(err.Error())
	}

	// caller must free the string
	return C.CString(str), nil
}
func FileSequence_Format(id FileSeqId, tpl *C.char) (*C.char, Error) {
	fs, ok := sFileSeqs.Get(id)
	if !ok {
		return C.CString(""), nil
	}

	str, err := fs.Format(C.GoString(tpl))
	if err != nil {
		return nil, C.CString(err.Error())
	}

	// caller must free the string
	return C.CString(str), nil
}
//export FileSequence_Format