code: public function Form($object)
      {
          $placeholder = _t(__CLASS__ . '.Placeholder', 'Add comments (optional)');
          $title = _t(__CLASS__ . '.MarkAsReviewedAction', 'Mark as reviewed');
  
          $fields = FieldList::create([
              HiddenField::create('ID', null, $object->ID),
              HiddenField::create('ClassName', null, $object->baseClass()),
              TextareaField::create('Review', '')
                  ->setAttribute('placeholder', $placeholder)
                  ->setSchemaData(['attributes' => ['placeholder' => $placeholder]])
          ]);
  
          $action = FormAction::create('savereview', $title)
              ->setTitle($title)
              ->setUseButtonTag(false)
              ->addExtraClass('review-content__action btn btn-primary');
          $actions = FieldList::create([$action]);
  
          $form = Form::create($this->controller, $this->name, $fields, $actions)
              ->setHTMLID('Form_EditForm_ReviewContent')
              ->addExtraClass('form--no-dividers review-content__form');
  
          return $form;
      }
docs: Bootstrap the form fields for the content review modal
  
  @param DataObject $object
  @return Form