php - Get Template Directory Timber/Twig -

i have setup simple twig template used display simple menu. have images in here static , use template directory path image src. when use {{theme.link}} appears blank. perhaps i'm referencing incorrectly. code below:

<?php        $context['menu'] = new timbermenu('main-nav');       timber::render('templates/menu.twig', $context);    ?> 

and twig template below:

 <ul>     {% item in menu.get_items %}     <li class="{{item.classes | join(' ')}}">       <a href="{{item.get_link}}">{{item.title}}</a>     </li>     {% endfor %}  </ul>  <img src="{{theme.link}}/assets/images/test.png" alt=""> 

i understand can pass in directory context i'm curios why built in function isn't working. simple. first time looking twig still getting used it. appreciated! thanks

@verdond2: in order use {{theme}} object (and properties) need start default timber context in php file...

<?php   $context = timber::get_context();   $context['menu'] = new timbermenu('main-nav');   timber::render('templates/menu.twig', $context);   ?>