public function addToOtherGroup($element)
    {
        if ($element instanceof \Zend_Form_Element) {
            if ($group = $this->getDisplayGroup(self::GROUP_OTHER)) {
                $group->addElement($element);
            } else  {
                $this->addDisplayGroup(array($element), self::GROUP_OTHER);
            }
        }
        return $this;
    }