def _has_frozen_base_class(cls):
        """
        Check whether *cls* has a frozen ancestor by looking at its
        __setattr__.
        """
        return (
            getattr(cls.__setattr__, "__module__", None)
            == _frozen_setattrs.__module__
            and cls.__setattr__.__name__ == _frozen_setattrs.__name__
        )

        Check whether *cls* has a frozen ancestor by looking at its
        __setattr__.
        
stackoverflow/venv/lib/python3.6/site-packages/attr/_make.py