public function modified($options = [])
    {
        $options += ['embed' => false];

        if ($this->_modified) {
          return true;
        }

        foreach ($this->_data as $index => $entity) {
            if (is_object($entity) && method_exists($entity, 'modified') && $entity->modified($options)) {
                return true;
            }
        }
        return false;
    }