code: public function init(){
          parent::init();        
          //$this->options = array_merge($this->options,['readonly'=>'true']);
          if($this->data){
              $order = 0;
              if(is_array($this->model->{$this->attribute})){
                  //echo '<pre>';
                  //print_r($this->model->{$this->attribute});die;
                  foreach($this->model->{$this->attribute} as $value){
                      $order++;
                      if(is_object($value)){
                          $this->options['options'][$value->Id] = ['data-order' => $order];
                      }else{
                          $this->options['options'][$value] = ['data-order' => $order];
                      }
                  }
              }
          }
      }
docs: Initializes the widget
  
  @throw InvalidConfigException