protected function _parseArg($argument, $args)
    {
        if (empty($this->_args)) {
            $args[] = $argument;

            return $args;
        }
        $next = count($args);
        if (!isset($this->_args[$next])) {
            throw new ConsoleException('Too many arguments.');
        }

        if ($this->_args[$next]->validChoice($argument)) {
            $args[] = $argument;

            return $args;
        }
    }