langchain/llms/bananadev.py/Banana/validate_environment
class Banana:    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that api key and python package exists in environment."""
        banana_api_key = get_from_dict_or_env(
            values, "banana_api_key", "BANANA_API_KEY"
        )
        values["banana_api_key"] = banana_api_key
        return values