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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 _related_items_changed(self, **kwargs):
 """ Ensure that the given related item is actually for the model this field applies to, and pass the instance to the real ``related_items_changed`` handler. """

        for_model = kwargs["instance"].content_type.model_class()
        if for_model and issubclass(for_model, self.model):
            instance_id = kwargs["instance"].object_pk
            try:
                instance = for_model.objects.get(id=instance_id)
            except self.model.DoesNotExist:
                # Instance itself was deleted - signals are irrelevant.
                return
            if hasattr(instance, "get_content_model"):
                instance = instance.get_content_model()
            related_manager = getattr(instance, self.related_field_name)
            self.related_items_changed(instance, related_manager)