code: public void visitComments(NodeVisitor visitor) {
          if (comments != null) {
              for (Comment c : comments) {
                  visitor.visit(c);
              }
          }
      }
docs: Visits the comment nodes in the order they appear in the source code.
  The comments are not visited by the {@link #visit} function - you must
  use this function to visit them.
  @param visitor the callback object.  It is passed each comment node.
  The return value is ignored.