code: public static <DATATYPE, ITEMTYPE extends ITreeItem <DATATYPE, ITEMTYPE>> void sort (@Nonnull final IBasicTree <? extends DATATYPE, ITEMTYPE> aTree,
                                                                                         @Nonnull final Comparator <? super DATATYPE> aValueComparator)
    {
      _sort (aTree, Comparator.comparing (IBasicTreeItem::getData, aValueComparator));
    }
docs: Sort each level of the passed tree with the specified comparator.
  
  @param aTree
  The tree to be sorted.
  @param aValueComparator
  The comparator to be used for sorting the tree items on each level.
  @param <DATATYPE>
  The tree item data type
  @param <ITEMTYPE>
  The tree item type