public function addArgument($name, $mode = null, $description = '', $default = null)
    {
        if (null === $mode) {
            $mode = self::OPTIONAL;
        } elseif (!is_int($mode) || $mode > 7 || $mode < 1) {
            throw new \InvalidArgumentException(sprintf('Argument mode "%s" is not valid.', $mode));
        }

        $this->arguments[] = [$name, $mode, $description, $default];
    }