private function getGroupId(): ?string
    {
        $group = $this->getPanelGroup();
        if (!$group) {
            return null;
        }

        $cssID = StringUtil::deserialize($group->cssID, true);
        if (is_string($cssID[0]) && $cssID[0] !== '') {
            return $cssID[0];
        }

        return 'panel-group-' . $group->id;
    }