private function traverseForVisitor(Twig_NodeVisitorInterface $visitor, Twig_Node $node)
{
$node = $visitor->enterNode($node, $this->env);
foreach ($node as $k => $n) {
if (false !== ($n = $this->traverseForVisitor($visitor, $n))) {
$node->setNode($k, $n);
} else {
$node->removeNode($k);
}
}
return $visitor->leaveNode($node, $this->env);
}