code: def get_for_resource(resource):
          
          resource_content_type = ContentType.objects.get_for_model(resource)
          default_items = set(DefaultPriceListItem.objects.filter(resource_content_type=resource_content_type))
          service = resource.service_project_link.service
          items = set(PriceListItem.objects.filter(
              default_price_list_item__in=default_items, service=service).select_related('default_price_list_item'))
          rewrited_defaults = set([i.default_price_list_item for i in items])
          return items | (default_items - rewrited_defaults)
docs: Get list of all price list items that should be used for resource.
  
              If price list item is defined for service - return it, otherwise -
              return default price list item.