How to get QDBusObjectPath in DBus?

I have a problem in extracting the returned value from a method called on DBus,
here is my code:

    QDBusPendingReply <QDBusObjectPath> reply = m_sysroot->GetOS(QStringLiteral("fedora"));
        reply.waitForFinished();
        if(! reply.isError()){
          qWarning() << "No Error" << Qt::endl;
          qWarning() << reply.argumentAt(0)<<Qt::endl;
        }
        else{
          qWarning() <<"Error occurs" << Qt::endl;
        }

here is the defination of GetOS:

<method name="GetOS">
      <arg name="name" type="s"/>
      <arg name="object_path" type="o" direction="out"/>
</method>

The output of the code is:

No Error

QVariant(QDBusObjectPath, )

How to get the object path ?? thanks

I have solved the problem by adding these 2 lines:

QDBusObjectPath objectPath = reply.argumentAt(0).value<QDBusObjectPath>();
 qWarning() << objectPath.path() << Qt::endl;