code: def set_sort_order(self, sort_order):
          
  
          if not isinstance(sort_order, SortOrder):
              raise DaftException("sort_order should be an instance of SortOrder.")
  
          self._sort_order = str(sort_order)
docs: Use the SortOrder object to sort the listings descending or ascending.
          :param sort_order:
          :return: