private static function _get_db(): ?bbn\db
  {
    if ( self::$db && self::$db->check() ){
      return self::$db;
    }
    return null;
  }
private static function _get_db(): ?bbn\db
  {
    if ( self::$db && self::$db->check() ){
      return self::$db;
    }
    return null;
  }
private static function _get_db ( ) : ? bbn \ db { if ( self :: $ db && self :: $ db -> check ( ) ) { return self :: $ db ; } return null ; }
Returns the database connection object.

@return bbn\db
Returns the database connection object .