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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def for_object(self, instance, flag=''):
 """ Filter to a specific instance. """

        check(instance)
        content_type = ContentType.objects.get_for_model(instance).pk
        queryset = self.filter(content_type=content_type, object_id=instance.pk)
        if flag:
            queryset = queryset.filter(flag=flag)
        return queryset