public function bulkSave($collection = [])
    {
        $params = [];

        $defaultIndex = $this->connection->getDefaultIndex();

        foreach ($collection as $item) {
            $modelIndex = $item->getDocumentIndex();

            $params['body'][] = [
                'index' => [
                    '_id'    => $item->getKey(),
                    '_type'  => $item->getDocumentType(),
                    '_index' => $modelIndex ? $modelIndex : $defaultIndex,
                ],
            ];
            $params['body'][] = $item->getDocumentData();
        }

        return $this->connection->bulkStatement($params);
    }