python - Replace list comprehension with FK lookup -

I currently have an understanding of the following list:

  [item.service.name For OrderItem.objects.all ()], there is an FK  OrderItem  at   
  service , hence the above code tones and tons  
 
 How to find any of the following questions? What do you want:  
  OrderItem.objects.values_list ('service__name', flat = true) .distinct ()