def validate_args(self):
        from .mixins import ModelMixin

        for arg in ('instance', 'decider', 'identifier', 'fields', 'default_language'):
            if getattr(self, arg) is None:
                raise AttributeError('%s must not be None' % arg)

        if not isinstance(self.instance, (ModelMixin,)):
            raise ImproperlyConfigured('"instance" argument must be a Linguist model')

        if not issubclass(self.decider, (models.Model,)):
            raise ImproperlyConfigured('"decider" argument must be a valid Django model')
Return a string formatted according to the :RFC:`3339`. If called with
dataset/ETHPy150Open ulule/django-linguist/linguist/fields.py/Linguist.validate_args--crossover with--dataset/ETHPy150Open eugenkiss/Simblin/simblin/lib/rfc3339.py/rfc3339