@Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
<p>Visits this <code>TraceNode</code> and all of its descendants in depth-first, prefix order.</p>

@param visitor The visitor to accept.
@return The <code>visitor</code> parameter.
vespajlib/src/main/java/com/yahoo/yolean/trace/TraceNode.java