if "reduce_documents_chain" in values:
                raise ValueError(
                    "Both `reduce_documents_chain` and `combine_document_chain` "
                    "cannot be provided at the same time. `combine_document_chain` "
                    "is deprecated, please only provide `reduce_documents_chain`"
                )
            combine_chain = values["combine_document_chain"]
            collapse_chain = values.get("collapse_document_chain")
            reduce_chain = ReduceDocumentsChain(
                combine_documents_chain=combine_chain,
                collapse_documents_chain=collapse_chain,
            )
            values["reduce_documents_chain"] = reduce_chain
            del values["combine_document_chain"]
            if "collapse_document_chain" in values:
                del values["collapse_document_chain"]
        return values
    @root_validator(pre=True)
    def get_return_intermediate_steps(cls, values: Dict) -> Dict:
        """For backwards compatibility."""
        if "return_map_steps" in values:
            values["return_intermediate_steps"] = values["return_map_steps"]
            del values["return_map_steps"]
        return values
    @root_validator(pre=True)
    def get_default_document_variable_name(cls, values: Dict) -> Dict:
        """Get default document variable name, if not provided."""
        if "document_variable_name" not in values:
            llm_chain_variables = values["llm_chain"].prompt.input_variables
            if len(llm_chain_variables) == 1:
                values["document_variable_name"] = llm_chain_variables[0]
            else:
                raise ValueError(
                    "document_variable_name must be provided if there are "
                    "multiple llm_chain input_variables"
                )
        else:
            llm_chain_variables = values["llm_chain"].prompt.input_variables