new_contents: from django.contrib.contenttypes.models import ContentType
  
  
  def reset_polymorphic_ctype(*models, **filters):
      """
      Set the polymorphic content-type ID field to the proper model
      Sort the ``*models`` from base class to descending class,
      to make sure the content types are properly assigned.
  
      Add ``preserve_existing=True`` to skip models which already
      have a polymorphic content type.
      """
      preserve_existing = filters.pop('preserve_existing', False)
      for new_model in models:
          new_ct = ContentType.objects.get_for_model(new_model)
  
          qs = new_model.objects.all()
          if preserve_existing:
              qs = qs.filter(polymorphic_ctype__isnull=True)
          if filters:
              qs = qs.filter(**filters)
          qs.update(polymorphic_ctype=new_ct)
  
subject: Add reset_polymorphic_ctype() function to assist with migration to polymorphic