Load pythonizations for ROOT>=6.22/00 (used for TTree in readCounters)
Since getattr(TTree, branch-name)
is also likely to be used in user code, it's probably more convenient to trigger the loading of pythonizations in any case (rather than forcing to do it ad-hoc, as originally done in https://gitlab.cern.ch/cp3-cms/bamboo/-/merge_requests/116 )