/**
  * Add twig extension
  * 
  * @param \Twig_ExtensionInterface $extension
  * 
  * @return \Bridge\Bundle\TwigBundle\TwigTemplating
  */
 public function addExtension(\Twig_ExtensionInterface $extension)
 {
     if ($extension instanceof ContainerAwareInterface) {
         $extension->setContainer($this->container);
     }
     if ($extension instanceof AbstractExtension) {
         $extension->setEngine($this->twigEngine);
     }
     $this->environment->addExtension($extension);
     return $this;
 }