def METHOD_NAME(self, file_name: Text, model_dir: Text) -> Optional[Dict[Text, Any]]:
    """Persist this model into the passed directory."""
    vector_file_name = file_name + "_vector.db"
    data_file_name = file_name + "_data.pkl"
    if self.vector and self.data:
        faiss.write_index(self.vector, os.path.join(model_dir, vector_file_name))
        io_utils.json_pickle(
            os.path.join(model_dir, data_file_name), self.data
        )
    return {"vector": vector_file_name, "data": data_file_name}