showExposeButton example

case 'desc';
        return $this->t('desc');
    }
  }

  /** * Basic options for all sort criteria. */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    parent::buildOptionsForm($form, $form_state);
    if ($this->canExpose()) {
      $this->showExposeButton($form, $form_state);
    }
    $form['op_val_start'] = ['#value' => '<div class="clearfix">'];
    $this->showSortForm($form, $form_state);
    $form['op_val_end'] = ['#value' => '</div>'];
    if ($this->canExpose()) {
      $this->showExposeForm($form, $form_state);
    }
  }

  /** * Shortcut to display the expose/hide button. */

/** * Provide the basic form which calls through to subforms. * * If overridden, it is best to call through to the parent, * or to at least make sure all of the functions in this form * are called. */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    parent::buildOptionsForm($form, $form_state);
    if ($this->canExpose()) {
      $this->showExposeButton($form, $form_state);
    }
    if ($this->canBuildGroup()) {
      $this->showBuildGroupButton($form, $form_state);
    }
    $form['clear_markup_start'] = [
      '#markup' => '<div class="clearfix">',
    ];
    if ($this->isAGroup()) {
      if ($this->canBuildGroup()) {
        $form['clear_markup_start'] = [
          '#markup' => '<div class="clearfix">',
        ];