def METHOD_NAME(self, action):
    if not action.option_strings:
        metavar, = self._metavar_formatter(action, action.dest)(1)
        return metavar
    else:
        parts = []
        # if the Optional doesn't take a value, format is:
        #    -s, --long
        if action.nargs == 0:
            parts.extend([self._bold(action_str) for action_str in action.option_strings])
        # if the Optional takes a value, format is:
        #    -s ARGS, --long ARGS
        else:
            default = self._underline(action.dest.upper())
            args_string = self._format_args(action, default)
            for option_string in action.option_strings:
                parts.append('%s %s' % (self._bold(option_string), args_string))
        return ', '.join(parts)