code: protected function process(array $nav)
      {
          // convert slugs to urls
          foreach ($nav as $key => $value) {
              // if the url is not set
              if (!isset($value['url'])) {
                  // set the url based on the slug
                  $nav[$key]['url'] = $this->url->to($value['slug']);
              }
              // remove any remaining slugs
              unset($nav[$key]['slug']);
          }
  
          // spit out the nav bar array at the end
          return $nav;
      }
docs: Convert slugs to urls.
  
  @param array $nav
  
  @return array