code: protected function removeNodeFilter(Twig_Node $node)
      {
          if ($node instanceof Twig_Node_Expression_Filter) {
              return $this->removeNodeFilter($node->getNode('node'));
          }
  
          return $node;
      }
docs: Removes node filters.
  
  This is mostly needed when another visitor adds filters (like the escaper one).
  
  @return Twig_Node