def shorten(msg: str, max_len: int=100) -> str:
    """
        Shorten this string, if longer than max_len, truncate and add "..."

    :param msg: the message to shorten
    :param max_len: the maximum length for this string
    :return: the shortened string
    """
    msg = str(msg)
    return msg if len(msg) < max_len else msg[:max_len] + '...'