public static function fromUrl($cssUrl, $baseUrl, $mediaType = 'all')
    {
        // Match URL.
        if (strpos($cssUrl, $baseUrl) === false) {
            throw new \InvalidArgumentException('The CSS URL does not begin with the base URL');
        }

        // Create.
        $baseLength = strlen(rtrim($baseUrl, '/')) + 1;
        $path = substr($cssUrl, $baseLength);
        return new CssResource($path, $mediaType);
    }