/**
  * Get raw edmsMongoDb instance
  *
  * @return edmsMongoDb
  */
 public static function instance($connectionId)
 {
     if (!isset(self::$_instance)) {
         self::$_instance = array();
     }
     if (!isset(self::$_instance[$connectionId])) {
         $component = Yii::app()->getComponent($connectionId);
         if ($component instanceof EDMSConnection) {
             self::$_instance[$connectionId] = $component;
         } else {
             //use YiiMongoDbSuite EMongoDB config
             if ($component instanceof EMongoDB) {
                 $connection = new EDMSConnection();
                 $connection->server = $component->connectionString;
                 $connection->dbName = $component->dbName;
                 if ($component->autoConnect == false) {
                     $connection->options['connect'] = false;
                 }
                 self::$_instance[$connectionId] = $connection;
             } else {
                 throw new EDMSException("Invalid connectionId: {$connectionId}");
             }
         }
     }
     return self::$_instance[$connectionId];
 }