void Test_RooNDKeysPdf() {
  // Simple macro to test the writeability of RooNDKeysPdf
  using namespace RooFit ;

  // Define two variables
  RooRealVar x("x","x",0,20) ;
  RooRealVar y("y","y",0,20) ;

  // Define two model for 1D
  RooPolynomial px("px","px",x,RooArgList(RooConst(0.03),RooConst(-0.01),RooConst(0.00032))) ;
  RooPolynomial py("py","py",y,RooArgList(RooConst(0.01),RooConst(0.01),RooConst(-0.0004))) ;

  // Combine them into a 2D model
  RooProdPdf pxy("pxy","pxy",RooArgSet(px,py)) ;

  // Create a dataset from this model
  RooDataSet* data = pxy.generate(RooArgSet(x,y),1000) ;

  // Create a histogram of the data
  TH1* hh_data = data->createHistogram("hh_data",x,Binning(10),YVar(y,Binning(10))) ;

  // Create 2D adaptive kernel estimation pdf with mirroring 
  RooNDKeysPdf kest("kest","kest",RooArgSet(x,y),*data,"am") ;

  // Create histogram of the 2d kernel estimation pdfs
  TH1* hh_pdf = kest.createHistogram("hh_pdf",x,Binning(50),YVar(y,Binning(50))) ;
  hh_pdf->SetLineColor(kBlue) ;

  TCanvas* c = new TCanvas("Test_RooNDKeysPdf","Test_RooNDKeysPdf",800,800) ;
  gPad->SetLeftMargin(0.15) ;
  hh_data->GetZaxis()->SetTitleOffset(1.2) ;
  hh_data->Draw("lego") ;
  hh_pdf->Draw("surfsame") ;
  c->Draw();

  // So far, so good

  // This won't work
  TFile* fout= TFile::Open("fout.root","RECREATE");
  kest.Write();
  fout->Close();

  // This won't work either
  // Create a new empty workspace
  RooWorkspace *w = new RooWorkspace("w","workspace") ;

  // Import model and all its components into the workspace
  w->import(pxy) ;

  // Import data into the workspace
  w->import(*data) ;

  // Import RooNDKeysPdf
  //w->import(kest);

  // Print workspace contents
  w->Print() ;

  // S a v e   w o r k s p a c e   i n   f i l e
  // -------------------------------------------

  // Save the workspace into a ROOT file
  w->writeToFile("rf502_workspace.root") ;


  // Workspace will remain in memory after macro finishes
  gDirectory->Add(w) ;
}