'Unregisters the given model(s).
If a model isn\'t already registered, this will raise NotRegistered.'

def unregister(self, model_or_iterable):

    if issubclass(model_or_iterable, models.Model):
        model_or_iterable = [model_or_iterable]
    for model in model_or_iterable:
        if (model not in self.registry):
            raise NotRegistered(('The    model    %s    is    not    registered' % model.__name__))
        del self.registry[model]
