def get_language_code(self):
        raise NotImplementedError("Subclasses of CommCareMobileContactMixin must implement method get_language_code().")
This method should be implemented by all subclasses of CommCareMobileContactMixin,
dataset/ETHPy150Open dimagi/commcare-hq/corehq/apps/sms/mixin.py/CommCareMobileContactMixin.get_language_code