code: private static void flattenCommentTree(List<CommentTreeElement> commentTree, List<CommentTreeElement> target) {
          for (CommentTreeElement c : commentTree) {
              target.add(c);
              if (c instanceof Comment) {
                  flattenCommentTree(((Comment)c).getReplies(), target);
              }
          }
      }
docs: Flatten the comment tree.
  The original comment tree is not overwritten.
  
  @param cs        List of comments that you get returned from one of the other methods here
  @param target    List in which to place the flattened comment tree.