docs: def create_items(sender, instance, **kwargs):
      """
      When one of the defined objects is created, initialize also its item.
      """
      if instance.item_id is None and instance.item is None:
          item = Item()
          if hasattr(instance, 'active'):
              item.active = getattr(instance, 'active')
          item.save()
          instance.item = item