public function init()
 {
     $attributes = $this->attributes;
     foreach ($attributes as $attribute => $options) {
         if (isset($options['handler'])) {
             $handler = $options['handler'];
             unset($options['handler']);
         } else {
             $handler = FileHandler::className();
         }
         $this->attributes[$attribute] = new $handler(['attribute' => $attribute, 'behavior' => $this, 'options' => $options]);
     }
 }