operatorForm example

$this->submitExposeForm($form, $form_state);
    }
    if ($this->isAGroup()) {
      $this->buildGroupSubmit($form, $form_state);
    }
  }

  /** * Shortcut to display the operator form. */
  public function showOperatorForm(&$form, FormStateInterface $form_state) {
    $this->operatorForm($form, $form_state);
    $form['operator']['#prefix'] = '<div class="views-group-box views-left-30">';
    $form['operator']['#suffix'] = '</div>';
  }

  /** * Options form subform for setting the operator. * * This may be overridden by child classes, and it must * define $form['operator']; * * @see buildOptionsForm() */