code: def get_for_model(self, model):
          
          return self.get_or_create(
              content_type    = ContentType.objects.get_for_model(model),
              object_id       = model.pk
          )
docs: Returns tuple (Entry instance, created) for specified
          model instance.
  
          :rtype: wagtailplus.wagtailrelations.models.Entry.