title: How to use Namespaced Sessions in Symfony2
body: <p>I am trying to use symfony2 sessions.I do this</p>
  
  <pre><code>    $session = $this-&gt;getRequest()-&gt;getSession();
      $session-&gt;set('token','value');
  </code></pre>
  
  <p>This works. But i want to use namespace in session. Documentation says </p>
  
  <pre><code>    class NamespacedAttributeBag 
  </code></pre>
  
  <p>provides that feature but i cannot figure out how to implement it</p>