langchain/llms/openai.py/BaseOpenAI/validate_environment
class BaseOpenAI:    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that api key and python package exists in environment."""
        openai_api_key = get_from_dict_or_env(
            values, "openai_api_key", "OPENAI_API_KEY"
        )
        openai_api_base = get_from_dict_or_env(
            values,
            "openai_api_base",
            "OPENAI_API_BASE",
            default="",
        )
        openai_proxy = get_from_dict_or_env(
            values,
            "openai_proxy",
            "OPENAI_PROXY",
            default="",
        )
        openai_organization = get_from_dict_or_env(
            values,
            "openai_organization",
            "OPENAI_ORGANIZATION",
            default="",
        )
        try:
            import openai

            openai.api_key = openai_api_key
            if openai_api_base:
                openai.api_base = openai_api_base
            if openai_organization:
                openai.organization = openai_organization
            if openai_proxy:
                openai.proxy = {"http": openai_proxy, "https": openai_proxy}  # type: ignore[assignment]  # noqa: E501
            values["client"] = openai.Completion
        except ImportError:
            raise ImportError(
                "Could not import openai python package. "
                "Please install it with `pip install openai`."
            )
        if values["streaming"] and values["n"] > 1:
            raise ValueError("Cannot stream results when n > 1.")
        if values["streaming"] and values["best_of"] > 1:
            raise ValueError("Cannot stream results when best_of > 1.")
        return values