code: public function normalizeRoute($route)
      {
          if ($this->action === null) {
              return $route;
          } elseif ($this->action === static::ACTION_REDIRECT_PERMANENT || $this->action === static::ACTION_REDIRECT_TEMPORARY) {
              throw new UrlNormalizerRedirectException([$route[0]] + $route[1], $this->action);
          } elseif ($this->action === static::ACTION_NOT_FOUND) {
              throw new NotFoundHttpException(Yii::t('yii', 'Page not found.'));
          } elseif (is_callable($this->action)) {
              return call_user_func($this->action, $route, $this);
          }
  
          throw new InvalidConfigException('Invalid normalizer action.');
      }
docs: Performs normalization action for the specified $route.
  @param array $route route for normalization
  @return array normalized route
  @throws InvalidConfigException if invalid normalization action is used.
  @throws UrlNormalizerRedirectException if normalization requires redirection.
  @throws NotFoundHttpException if normalization suggests action matching route does not exist.