def serialize_search(self, pid_fetcher, search_result, links=None,
                         item_links_factory=None):
        """Serialize a search result.

        :param pid_fetcher: Persistent identifier fetcher.
        :param search_result: Elasticsearch search result.
        :param links: Dictionary of links to add to response.
        """
        records = []
        for hit in search_result['hits']['hits']:
            records.append(self.schema.tostring(self.transform_search_hit(
                pid_fetcher(hit['_id'], hit['_source']),
                hit,
                links_factory=item_links_factory,
            )))

        return "\n".join(records)