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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 marking_thru(self):
 """ Return the back-pointer to markings that may have been attached via Django's content type mechanism. """

        self_django_type = ContentType.objects.get_for_model(self)
        return Marking2X.objects.filter(content_type__pk=self_django_type.id,
                                        object_id=self.id)