function whoisIdentifier($type, $value)
    {
        $response = $this->call( new Command\Members\Whois($type, $value) );
        if ( $ex = $response->hasException() )
            throw $ex;


        if ($response->getResponseCode() === 204)
            // No Identifier with given type, value match.
            return null;

        $r = $response->expected();
        $r = ($r instanceof iDataEntity) ? $r->get('result') : $r;
        return $r;
    }