code: public function addCallback($callback, $data = [], $region = "main", $sort = 0)
      {
          $view = new View();
          $view->set(["callback" => $callback], $data, $sort, "callback");
          $this->views[$region][] = $view;
  
          return $this;
      }
docs: Add a callback to be rendered as a view.
  
  @param string $callback function to call to get the content of the view
  @param array  $data     variables to make available to the view, default is empty
  @param string $region   which region to attach the view
  @param int    $sort     which order to display the views
  
  @return $this