public function setVisible(string $visible = "T") : CNabuDataObject
    {
        if ($visible === null) {
            throw new ENabuCoreException(
                    ENabuCoreException::ERROR_NULL_VALUE_NOT_ALLOWED_IN,
                    array("\$visible")
            );
        }
        $this->setValue('nb_site_map_visible', $visible);
        
        return $this;
    }