void Import_GDML_Export_ROOT()
{
  TGeoManager* gdml = new TGeoManager("gdml", "Trd Frame");
  
  
  TGDMLParse parser;
  // Define your input GDML file HERE
  TGeoVolume* gdmlTop = parser.GDMLReadFile("mainframe.gdml");

  TGeoVolume* rootTop = new TGeoVolumeAssembly("TRD_Mainframe");
  gGeoManager->SetTopVolume(rootTop);
  
  
  TObjArray *_node = gdmlTop->GetNodes();
  
       Int_t copy_number =0;
   for (int iNode = 0; iNode < _node->GetEntriesFast(); iNode++) {
   TGeoNode *_fNode = (TGeoNode *)_node->At(iNode);
   
      TGeoVolume *_fVol = (TGeoVolume *)_fNode->GetVolume();

      rootTop->AddNode(_fVol, copy_number, 0);
      copy_number++;
   }

  gGeoManager->CloseGeometry();
  // Define you output ROOT file HERE
  TFile* outfile = new TFile("mainframe.geo.root", "RECREATE");

  rootTop->Write();
  outfile->Close();
}