Parse command line options and set them to ``config``.

    This function skips unknown command line options. After parsing options,
    set log level and set options in ``tornado.options``.

def parse_command_line() -> Namespace:
    """Parse command line options and set them to ``config``.

    This function skips unknown command line options. After parsing options,
    set log level and set options in ``tornado.options``.
    """
    import tornado.options
    parser.parse_known_args(namespace=config)
    set_loglevel()  # set new log level based on commanline option
    for k, v in vars(config).items():
        if k.startswith('log'):
            tornado.options.options.__setattr__(k, v)
    return config