/**
  * Prepare security- and filter-based restrictions.
  * @access private
  */
 protected function _prepare_restrictions()
 {
     $this->_returns_no_data = !isset($this->_entry) || !$this->_entry->exists();
     if (!$this->_returns_no_data) {
         parent::_prepare_restrictions();
         $this->_calculated_restrictions[] = "etob.entry_id = {$this->_entry->id}";
     }
 }