public function render($type, $assets)
    {
        if (! in_array($type, $this->types)) {
            throw new InvalidArgumentException("Invalid assets type [${type}]");
        }

        // The assets type is valid.
        else if (! empty($items = $this->parseAssets($assets))) {
            return implode("\n", $this->renderItems($items, $type, false));
        }
    }