Ownership of TTree is shared between RooFit and file after writing a RooDataSet

import ROOT

ws = ROOT.RooWorkspace('ws')  # workspace to store fit results, etc.

x = ROOT.RooRealVar('x', 'x', 0)  # generate some data in this dimension later

fs = ROOT.TFile('store.root', 'RECREATE')

ROOT.RooAbsData.setDefaultStorageType(ROOT.RooAbsData.Tree)  # use Tree-backed data store

data = ROOT.RooDataSet('data', 'data', ROOT.RooArgSet(x))

for v in range(1000):  # fill dataset with very meaningful data

    x.setVal(v)

    data.add(ROOT.RooArgSet(x))

getattr(ws, 'import')(data)  # add dataset to workspace

                             # `import` is a python keyword, need to use `getattr`

ws.Print('v')  # check that everything looks as expected

wf = ROOT.TFile('ws.root', 'RECREATE')  # save workspace to this file

ws.Write()

wf.Close()  # this seems to be part of the problem

# when leaving wf opened and deleting `ws` and `data`, there is no segfault

# del ws, data 

print('Done!')  # the segfault appears after this line