protected function renderDropDownList($name, $value, $options)
    {
        if ($this->renderer->isBootstrapTheme()) {
            Html::addCssClass($options, 'form-control');
        }

        $options['tabindex'] = self::TABINDEX;

        return Html::dropDownList($name, $value, $this->prepareItems($this->items), $options);
    }