def _replacement(name, default):
        # type: (Text, Optional[Text]) -> Text
        """
        get appropriate value for a variable name.
        first search in environ, if not found,
        then look into the dotenv variables
        """
        default = default if default is not None else ""
        ret = os.getenv(name, new_values.get(name, default))
        return ret  # type: ignore

        get appropriate value for a variable name.
        first search in environ, if not found,
        then look into the dotenv variables
        
dynaconf/vendor/dotenv/main.py