/**
  * Release any resourced held by this form storage mechanism for the indicated form
  * @param string $form
  */
 public function release($form)
 {
     if (!is_string($form)) {
         return;
     }
     if (array_key_exists($form, $this->locations)) {
         unset($this->locations[$form]);
     }
     if (array_key_exists($form, $this->mod_time)) {
         unset($this->mod_time[$form]);
     }
     parent::release($form);
 }