get_default_document_variable_name() — langchain Function Reference

Source Code

libs/langchain/langchain_classic/chains/combine_documents/stuff.py lines 168–191

    def get_default_document_variable_name(cls, values: dict) -> Any:
        """Get default document variable name, if not provided.

        If only one variable is present in the llm_chain.prompt,
        we can infer that the formatted documents should be passed in
        with this variable name.
        """
        llm_chain_variables = values["llm_chain"].prompt.input_variables
        if "document_variable_name" not in values:
            if len(llm_chain_variables) == 1:
                values["document_variable_name"] = llm_chain_variables[0]
            else:
                msg = (
                    "document_variable_name must be provided if there are "
                    "multiple llm_chain_variables"
                )
                raise ValueError(msg)
        elif values["document_variable_name"] not in llm_chain_variables:
            msg = (
                f"document_variable_name {values['document_variable_name']} was "
                f"not found in llm_chain input_variables: {llm_chain_variables}"
            )
            raise ValueError(msg)
        return values