protected function getContentLocationIds($contentObjectId)
    {
        $query = $this->databaseHandler->createSelectQuery();
        $query->select('node_id')
            ->from($this->databaseHandler->quoteTable(self::CONTENTOBJECT_TREE_TABLE))
            ->where($query->expr->eq('contentobject_id', $contentObjectId));
        $stmt = $query->prepare();
        $stmt->execute();
        $nodeIds = $stmt->fetchAll(PDO::FETCH_COLUMN);

        return is_array($nodeIds) ? array_map('intval', $nodeIds) : [];
    }