code: @Nonnull
    public static <KEYTYPE, DATATYPE> DefaultFolderTree <KEYTYPE, DATATYPE, ICommonsSet <DATATYPE>> createForSet (@Nonnull final IAggregator <KEYTYPE, KEYTYPE> aKeyCombinator)
    {
      return new DefaultFolderTree <> (aKeyCombinator);
    }
docs: Create a new {@link DefaultFolderTree} using a set as the container.
  
  @param <KEYTYPE>
  The type of the element keys.
  @param <DATATYPE>
  The type of the elements contained in the tree
  @param aKeyCombinator
  The key combinator to be used
  @return The created default folder tree