code: public function getClientOptions($model, $attribute)
      {
          $pattern = Html::escapeJsRegularExpression($this->pattern);
  
          $options = [
              'pattern' => new JsExpression($pattern),
              'not' => $this->not,
              'message' => $this->formatMessage($this->message, [
                  'attribute' => $model->getAttributeLabel($attribute),
              ]),
          ];
          if ($this->skipOnEmpty) {
              $options['skipOnEmpty'] = 1;
          }
  
          return $options;
      }
docs: {@inheritdoc}