fetch_k: (Optional[int]) Number of Documents to fetch before filtering.
                      Defaults to 20.
        Returns:
            List of Documents most similar to the query.
        """
        docs_and_scores = self.similarity_search_with_score(
            query, k, filter=filter, fetch_k=fetch_k, **kwargs
        )
        return [doc for doc, _ in docs_and_scores]
[docs]    def max_marginal_relevance_search_by_vector(
        self,
        embedding: List[float],
        k: int = 4,
        fetch_k: int = 20,
        lambda_mult: float = 0.5,
        filter: Optional[Dict[str, Any]] = None,
        **kwargs: Any,
    ) -> List[Document]:
        """Return docs selected using the maximal marginal relevance.
        Maximal marginal relevance optimizes for similarity to query AND diversity
        among selected documents.
        Args:
            embedding: Embedding to look up documents similar to.
            k: Number of Documents to return. Defaults to 4.
            fetch_k: Number of Documents to fetch before filtering to
                     pass to MMR algorithm.
            lambda_mult: Number between 0 and 1 that determines the degree
                        of diversity among the results with 0 corresponding
                        to maximum diversity and 1 to minimum diversity.
                        Defaults to 0.5.
        Returns:
            List of Documents selected by maximal marginal relevance.
        """
        _, indices = self.index.search(
            np.array([embedding], dtype=np.float32),
            fetch_k if filter is None else fetch_k * 2,
        )
        if filter is not None:
            filtered_indices = []
            for i in indices[0]:
                if i == -1:
rtdocs_stable/api.python.langchain.com/en/stable/_modules/langchain/vectorstores/faiss.html