langchain/llms/gpt4all.py/GPT4All/validate_environment
class GPT4All:    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that the python package exists in the environment."""
        try:
            from gpt4all import GPT4All as GPT4AllModel

            full_path = values["model"]
            model_path, delimiter, model_name = full_path.rpartition("/")
            model_path += delimiter

            values["client"] = GPT4AllModel(
                model_name=model_name,
                model_path=model_path or None,
                model_type=values["backend"],
                allow_download=False,
            )
            values["backend"] = values["client"].model.model_type

        except ImportError:
            raise ValueError(
                "Could not import gpt4all python package. "
                "Please install it with `pip install gpt4all`."
            )
        return values