code: public static XNElement storeList(String container, String item, Iterable<? extends XNSerializable> source) {
          XNElement result = new XNElement(container);
          for (XNSerializable e : source) {
              e.save(result.add(item));
          }
          return result;
      }
docs: Create an XNElement with the given name and items stored from the source sequence.
  @param container the container name
  @param item the item name
  @param source the source of items
  @return the list in XNElement