private function ensureSiteMenus(Site $site)
    {
        $ret = [];

        if ($this->treeManager && $this->allowedMenus) {
            $storage = $this->treeManager->getMenuStorage();

            foreach ($this->allowedMenus as $prefix => $title) {

                $name = $prefix.'-'.$site->getId();

                if (!$storage->exists($name)) {
                    $ret[$name] = $storage->create($name, ['title' => $this->t($title), 'site_id' => $site->getId()]);
                }
            }
        }

        return $ret;
    }