def METHOD_NAME(self, arg):
    body = arg[len("--"):]
    if body == "debug":
        self.parsed.debug = True
        return
    if body == "help":
        self.parsed.help = True
        self.end_early = True
        return
    if body == "version":
        self.parsed.version = True
        self.end_early = True
        return
    if body == "gui":
        self.parsed.gui = True
        return
    self.error("Unrecognized option: {}".format(arg))