code: protected function formatMessage($message, $params)
      {
          if (Yii::$app !== null) {
              return \Yii::$app->getI18n()->format($message, $params, Yii::$app->language);
          }
  
          $placeholders = [];
          foreach ((array) $params as $name => $value) {
              $placeholders['{' . $name . '}'] = $value;
          }
  
          return ($placeholders === []) ? $message : strtr($message, $placeholders);
      }
docs: Formats a mesage using the I18N, or simple strtr if `\Yii::$app` is not available.
  @param string $message
  @param array $params
  @since 2.0.12
  @return string