langchain/chains/loading.py/_load_llm_chain
def _load_llm_chain(config: dict, **kwargs: Any) -> LLMChain:
    """Load LLM chain from config dict."""
    if "llm" in config:
        llm_config = config.pop("llm")
        llm = load_llm_from_config(llm_config)
    elif "llm_path" in config:
        llm = load_llm(config.pop("llm_path"))
    else:
        raise ValueError("One of `llm` or `llm_path` must be present.")

    if "prompt" in config:
        prompt_config = config.pop("prompt")
        prompt = load_prompt_from_config(prompt_config)
    elif "prompt_path" in config:
        prompt = load_prompt(config.pop("prompt_path"))
    else:
        raise ValueError("One of `prompt` or `prompt_path` must be present.")

    return LLMChain(llm=llm, prompt=prompt, **config)