public function getPackageAssetsDirs($jsonData)
    {
        $packagesAssetsDir = null;
        // If some assets were set on the package
        if (isset($jsonData["extra"][self::LABEL_ASSETS_DIR])) {
            // We get the assets-dir of this package
            $packagesAssetsDir = $jsonData["extra"][self::LABEL_ASSETS_DIR];
            if (is_string($packagesAssetsDir)) {
                // If we get a string, it's the public shortcut so we uniform the return
                $packagesAssetsDir = array(self::LABEL_PUBLIC_DIR => $packagesAssetsDir);
            }
        }
        return $packagesAssetsDir;
    }