code: public static function errorSummary($models, $options = [])
      {
          $showAllErrors = ArrayHelper::remove($options, 'showAllErrors', false);
          $lines = self::collectErrors($models, $showAllErrors);
  
          return implode(PHP_EOL, $lines);
      }
docs: Generates a summary of the validation errors.
  @param Model|Model[] $models the model(s) whose validation errors are to be displayed.
  @param array $options the tag options in terms of name-value pairs. The following options are specially handled:
  
  - showAllErrors: boolean, if set to true every error message for each attribute will be shown otherwise
  only the first error message for each attribute will be shown. Defaults to `false`.
  
  @return string the generated error summary
  @since 2.0.14