public function setLevel(int $level = 1) : CNabuDataObject
    {
        if ($level === null) {
            throw new ENabuCoreException(
                    ENabuCoreException::ERROR_NULL_VALUE_NOT_ALLOWED_IN,
                    array("\$level")
            );
        }
        $this->setValue('nb_site_map_level', $level);
        
        return $this;
    }