RETURN A FILENAME THAT CAN SERVE AS A BACKUP FOR THIS FILE

def backup_name(self, timestamp=None):
        """
        RETURN A FILENAME THAT CAN SERVE AS A BACKUP FOR THIS FILE
        """
        suffix = datetime2string(coalesce(timestamp, datetime.now()), "%Y%m%d_%H%M%S")
        return File.add_suffix(self._filename, suffix)