code: public function addErrors(array $items)
      {
          foreach ($items as $attribute => $errors) {
              if (is_array($errors)) {
                  foreach ($errors as $error) {
                      $this->addError($attribute, $error);
                  }
              } else {
                  $this->addError($attribute, $errors);
              }
          }
      }
docs: Adds a list of errors.
  @param array $items a list of errors. The array keys must be attribute names.
  The array values should be error messages. If an attribute has multiple errors,
  these errors must be given in terms of an array.
  You may use the result of [[getErrors()]] as the value for this parameter.
  @since 2.0.2