old_contents: from django.db.models import manager
  
  from .querysets import OrderableQueryset
  
  
  class OrderableManager(manager.BaseManager.from_queryset(OrderableQueryset)):
      pass
  
new_contents: from django.db.models import manager
  
  from .querysets import OrderableQueryset
  
  
  OrderableManager = manager.BaseManager.from_queryset(OrderableQueryset)
  
subject: Change Manager construction method