langchain/vectorstores/faiss.py/FAISS/load_local
class FAISS:    def load_local(
        cls, folder_path: str, embeddings: Embeddings, index_name: str = "index"
    ) -> FAISS:
        """Load FAISS index, docstore, and index_to_docstore_id to disk.

        Args:
            folder_path: folder path to load index, docstore,
                and index_to_docstore_id from.
            embeddings: Embeddings to use when generating queries
            index_name: for saving with a specific index file name
        """
        path = Path(folder_path)
        # load index separately since it is not picklable
        faiss = dependable_faiss_import()
        index = faiss.read_index(
            str(path / "{index_name}.faiss".format(index_name=index_name))
        )

        # load docstore and index_to_docstore_id
        with open(path / "{index_name}.pkl".format(index_name=index_name), "rb") as f:
            docstore, index_to_docstore_id = pickle.load(f)
        return cls(embeddings.embed_query, index, docstore, index_to_docstore_id)