public function getParentDsId($dsId)
    {
        if (!array_key_exists($dsId, $this->parentMap)) {
            throw new InvalidArgumentException('Unknown ds_id ', $dsId);
        }

        return $this->parentMap[$dsId];
    }
public function getParentDsId($dsId)
    {
        if (!array_key_exists($dsId, $this->parentMap)) {
            throw new InvalidArgumentException('Unknown ds_id ', $dsId);
        }

        return $this->parentMap[$dsId];
    }
public function getParentDsId ( $ dsId ) { if ( ! array_key_exists ( $ dsId , $ this -> parentMap ) ) { throw new InvalidArgumentException ( 'Unknown ds_id ' , $ dsId ) ; } return $ this -> parentMap [ $ dsId ] ; }
Get parent node by node id.

@param string $dsId

@return string

@throws InvalidArgumentException
Get parent node by node id .