Nette\Forms\Form::addGroup PHP Method

    public function addGroup($caption = NULL, $setAsCurrent = TRUE)
    {
        $group = new ControlGroup();
        $group->setOption('label', $caption);
        $group->setOption('visual', TRUE);
        if ($setAsCurrent) {
            $this->setCurrentGroup($group);
        }
        if (!is_scalar($caption) || isset($this->groups[$caption])) {
            return $this->groups[] = $group;
        } else {
            return $this->groups[$caption] = $group;
        }
    }

 /**
  * Email subscribers
  *
  * @return \Nette\Forms\Form
  */
 public static function email(array $get)
 {
     $form = new Form('adminEmail');
     // Prepare
     if (isset($get['action']) && $get['action'] == 'email') {
         $preFill = TRUE;
     } else {
         $preFill = FALSE;
     }
     $emailWhoDefault = $preFill ? 2 : 1;
     $emailSubscriberDefault = isset($get['email']) ? $get['email'] : '';
     // Email subscribers
     $form->addGroup('E-mail Subscriber(s)');
     $form->addSelect('emailWho', 'Recipient(s)', array(1 => 'All subscriber(s)', 2 => 'Single Subscriber', 3 => 'Wordpress Registered subscribers', 4 => 'Non-wordpress Registered subscribers'))->setDefaultValue($emailWhoDefault)->addCondition(Form::EQUAL, 2)->toggle("subscriber");
     $form->addGroup()->setOption('container', Html::el('fieldset')->id("subscriber"));
     $form->addText("email", "Subscriber")->setDefaultValue($emailSubscriberDefault)->addCondition(Form::FILLED)->addRule(Form::EMAIL, 'Must be valid e-mail address');
     $form->addGroup();
     $form->addText('subject', 'Subject')->setRequired('Subject is required');
     $form->addTextArea('body', 'E-mail message')->setRequired('You don\'t want to send an empty message now do you :)');
     // Submit
     $form->addSubmit('submit', 'Send')->setAttribute('class', 'button-primary');
     return $form;
 }