public function render()
    {
        $html = '';

        if (count($this->groupFields)) {
            foreach ($this->groupFields as $group) {
                $htmlControl = '';
                $fields = $group['fields'];

                foreach ($fields as $field) {
                    $htmlControl .= $field->render();
                }
                $label = $group['name'];
                $html .= sprintf($this->htmlItemTemplate, $label, $htmlControl);
            }
        }

        return $html;
    }