public function render()
    {
        $i = 0;
        $output = [];
        $count  = count($this->_items);
        foreach ($this->_items as $item) {
            $i++;
            $item['class'] = 'item-wrapper tb-item-' . $i;

            if ($i == 1) {
                $item['class'] .= ' first';
            }

            if ($i == $count) {
                $item['class'] .= ' last';
            }

            $output[] = $this->renderItem($item);
        }

        return implode(PHP_EOL, $output);
    }