langchain/chains/combine_documents/refine.py/RefineDocumentsChain/_construct_result
class RefineDocumentsChain:    def _construct_result(self, refine_steps: List[str], res: str) -> Tuple[str, dict]:
        if self.return_intermediate_steps:
            extra_return_dict = {"intermediate_steps": refine_steps}
        else:
            extra_return_dict = {}
        return res, extra_return_dict