code: public OrderingList<S> concat(Class<S> type, String property) {
          OrderingList<S> newList = this;
          if (newList == EMPTY_LIST) {
              // Cannot concat from singleton EMPTY_LIST.
              newList = getListHead(type);
          }
          return newList.nextNode(type, property);
      }
docs: Returns a list which concatenates this one with the given property.