public function icon($service, array $options = [])
    {
        $class = 'fa ' . (!empty($this->_fa[$service]) ? $this->_fa[$service] : $this->_config['default_fa']);
        if (!empty($options['icon_class'])) {
            $class = $options['icon_class'];
        }

        return '<i class="' . $class . '"></i>';
    }