Invoking sphere creation with C++ code only

Hello, dear Paraview developers!

  vtkSMSession* session = vtkSMSession::New();
  vtkSMSessionProxyManager* pxm = session->GetSessionProxyManager();
  vtkSMProxy* proxy = pxm->NewProxy("sources", "SphereSource");
  vtkSMPropertyHelper(proxy, "Radius").Set(4.2);
  vtkSMPropertyHelper(proxy, "Radius").Set(8.4);

I was trying to invoke sphere creation inside from my filter’s widget, following ParaView/Remoting/ServerManager/Testing/Cxx/vtkSMPropertyHelperTest.cxx at 6f7d870595bf68b02dcf63c1a56adf6eb53dd2f1 · OpenChemistry/ParaView · GitHub and dear Mathieu advices, but this code has not created any sphere.

Could you please give me an advice on how to accomplish it?

Best regards,