def _add_handler(cls, handler, fmt, level):
        """
        Args:
            handler (logging.Handler): Handler to decorate
            fmt (str | unicode): Format to use
        """
        handler.setFormatter(_get_formatter(fmt))
        if level:
            handler.setLevel(level)
        logging.root.addHandler(handler)
        cls.used_formats = ("%s %s" % (cls.used_formats or "", fmt)).strip()
        cls.handlers.append(handler)