protected function initializeAssetsVendorDir()
    {
        $path = $this->getRootPackageAssetsPath() . '/' . (
            $this->assets_vendor_dir ? str_replace($this->getRootPackageAssetsPath(), '', $this->assets_vendor_dir) : ''
        );
        $this->filesystem->ensureDirectoryExists($path);
        $this->assets_vendor_dir = realpath($path);
        return $this;
    }