sortSubmit example

  }

  /** * Simple submit handler. */
  public function submitOptionsForm(&$form, FormStateInterface $form_state) {
    // Do not store this values.     $form_state->unsetValue('expose_button');

    $this->sortSubmit($form, $form_state);
    if (!empty($this->options['exposed'])) {
      $this->submitExposeForm($form, $form_state);
    }
  }

  /** * Shortcut to display the value form. */
  protected function showSortForm(&$form, FormStateInterface $form_state) {
    $options = $this->sortOptions();
    if (!empty($options)) {