langchain/retrievers/elastic_search_bm25.py/ElasticSearchBM25Retriever/get_relevant_documents
class ElasticSearchBM25Retriever:    def get_relevant_documents(self, query: str) -> List[Document]:
        query_dict = {"query": {"match": {"content": query}}}
        res = self.client.search(index=self.index_name, body=query_dict)

        docs = []
        for r in res["hits"]["hits"]:
            docs.append(Document(page_content=r["_source"]["content"]))
        return docs