def _load_run_evaluators(
    config: smith_eval.RunEvalConfig,
    run_type: str,
    data_type: DataType,
    example_outputs: Optional[List[str]],
    run_inputs: Optional[List[str]],
    run_outputs: Optional[List[str]],
) -> List[RunEvaluator]:
    """
    Load run evaluators from a configuration.
    Args:
        config: Configuration for the run evaluators.
    Returns:
        A list of run evaluators.
    """
    run_evaluators = []
    input_key, prediction_key, reference_key = None, None, None
    if (
        config.evaluators
        or any([isinstance(e, EvaluatorType) for e in config.evaluators])
        or (
            config.custom_evaluators
            and any([isinstance(e, StringEvaluator) for e in config.custom_evaluators])
        )
    ):
        input_key, prediction_key, reference_key = _get_keys(
            config, run_inputs, run_outputs, example_outputs
        )
    for eval_config in config.evaluators:
        run_evaluator = _construct_run_evaluator(
            eval_config,
            config.eval_llm,
            run_type,
            data_type,
            example_outputs,
            reference_key,
            input_key,
            prediction_key,
        )
        run_evaluators.append(run_evaluator)
    custom_evaluators = config.custom_evaluators or []
    for custom_evaluator in custom_evaluators:
        if isinstance(custom_evaluator, RunEvaluator):
            run_evaluators.append(custom_evaluator)
        elif isinstance(custom_evaluator, StringEvaluator):
            run_evaluators.append(
                smith_eval.StringRunEvaluatorChain.from_run_and_data_type(