Get covariant matrix or confidence level from fitting result

Hi experts,

Sorry, I tried like ConfidenceIntervals.C or ErrorIntegral.C

TEfficiency *TEff = new TEff();
TVirtualFitter * fitter = TVirtualFitter::GetFitter();
assert(fitter != 0);
TH1D *test = new TH1D(“test”,“test”,50,0,250);
double * covMatrix = fitter->GetCovarianceMatrix();
Double_t Integral = f1->Integral(160,250)
Double_t Integral_err = f1->IntegralError(160,250)
cout<<Integral<<" "<<Integral_err<<endl;

but I got an error
Error in TBackCompFitter::GetConfidenceIntervals: Cannot compute confidence intervals with an invalide fit result
Warning in TBackCompFitter::GetCovarianceMatrix: Invalid fit result
Error in TF1Helper::IntegralError: Last used fitter is not compatible with the current TF1

I checked fit result but it is valid and its status is converged.
TBinomialEfficiencyFitter doesn’t support GetCovarianceMatrix and GetConfidenceIntervals ?