langchain/utilities/bing_search.py/BingSearchAPIWrapper/validate_environment
class BingSearchAPIWrapper:    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that api key and endpoint exists in environment."""
        bing_subscription_key = get_from_dict_or_env(
            values, "bing_subscription_key", "BING_SUBSCRIPTION_KEY"
        )
        values["bing_subscription_key"] = bing_subscription_key

        bing_search_url = get_from_dict_or_env(
            values,
            "bing_search_url",
            "BING_SEARCH_URL",
            # default="https://api.bing.microsoft.com/v7.0/search",
        )

        values["bing_search_url"] = bing_search_url

        return values