else:
            llm_chain_variables = values["llm_chain"].prompt.input_variables
            if values["document_variable_name"] not in llm_chain_variables:
                raise ValueError(
                    f"document_variable_name {values['document_variable_name']} was "
                    f"not found in llm_chain input_variables: {llm_chain_variables}"
                )
        return values
    @property
    def collapse_document_chain(self) -> BaseCombineDocumentsChain:
        """Kept for backward compatibility."""
        if isinstance(self.reduce_documents_chain, ReduceDocumentsChain):
            if self.reduce_documents_chain.collapse_documents_chain:
                return self.reduce_documents_chain.collapse_documents_chain
            else:
                return self.reduce_documents_chain.combine_documents_chain
        else:
            raise ValueError(
                f"`reduce_documents_chain` is of type "
                f"{type(self.reduce_documents_chain)} so it does not have "
                f"this attribute."
            )
    @property
    def combine_document_chain(self) -> BaseCombineDocumentsChain:
        """Kept for backward compatibility."""
        if isinstance(self.reduce_documents_chain, ReduceDocumentsChain):
            return self.reduce_documents_chain.combine_documents_chain
        else:
            raise ValueError(
                f"`reduce_documents_chain` is of type "
                f"{type(self.reduce_documents_chain)} so it does not have "
                f"this attribute."
            )
[docs]    def combine_docs(
        self,
        docs: List[Document],
        token_max: Optional[int] = None,
        callbacks: Callbacks = None,
        **kwargs: Any,
    ) -> Tuple[str, dict]:
        """Combine documents in a map reduce manner.
        Combine by mapping first chain over all documents, then reducing the results.