phptemplate to twig conversion

gistfile1.twig

    {% if main_menu %}
     <div id="main-menu" class="navigation">
       {{ theme('links__system_main_menu', {
         links: main_menu,
         attributes: {
           id: 'main-menu-links',
           class: [ links, clearfix ]
         },
         heading: {
           text: t('Main menu'),
           level: 'h2',
           class: [ 'element invisisble' ]
         }
       }) }}
      </div> <!-- /#main-menu -->
    {% endif %}