@SuppressWarnings("UnusedParameters")
    public void entering(TraceNode node) {
        // empty
    }
<p>Enters a {@link TraceNode}. This method is called after {@link #visit(TraceNode)}, but before visiting its
children. Note that this method is NOT called if a <code>TraceNode</code> has zero children.</p>
<p>The default implementation of this method does nothing.</p>

@param node the <code>TraceNode</code> being entered
@see #leaving(TraceNode)
vespajlib/src/main/java/com/yahoo/yolean/trace/TraceVisitor.java