v2dl3-vegas: Event Selection Patch

[tmcahill]

This patch utilizes the previously implemented "EventClass" object in order to select events to separate event lists and FITS files. New flags have been tested and output has been reproduced with no differences to main using fitsdiff.

Very little VEGAS-specific review here, so I've added a question about how we utilize VEGAS root data in the previous patch.

For VEGAS Review

• fillEVENTS_not_safe.py accesses additional selectedEventsTree attributes .fMSW and .fMSL in the manner specified by VEGAS docs
• From previous commit 6c6e3f2:
  • EventClass.py reads EA via VARootIO to get the cuts info ("pfCutsFileText" in the root file)
  • fCutsFileText is passed (as a string) to getCuts() in util.py to search for substrings matching the desired cut param names.
    • This seems to me to be a naive method, but I could not find info about this in the VEGAS docs. I did a fair amount of investigating the EA root files via VARootIO and uproot; it seems to me that cuts info is only available as raw text. However, if there is a VARootIO library method that parses this file for me, that is better to use so it will be paired to VEGAS updates.

Full Changelog

fillEVENTS.py

• Event class support when provided optional arg event_class_idx

• Appends MSW and MSL columns when appropriate

  fillRESPONSE.py

• Event class support when provided optional arg event_class_idx

  genHDUList.py

• Optional arguments added

  v2dl3_for_vegas.py

• -save_msw_msl flag added
• Extended fits output for event class mode as new helper function make_eclass_path()

• Extended index file output for event class mode as new helper function gen_index_files()

  VegasDataSource.py

• Support for event classes and save_msw_msl flag

  fillEVENTS_not_safe.py

• Now filters events to separate dicts when using >1 event class.
• Added MSW and MSL access from SelectedEventsTree

[tmcahill]

@cameronrulten @GernotMaier All paths now use os.path operations. I also renamed internal event_class variables to event_group related names to be more clear whether or not it is referring specifically to EventClass related operations. Changes are re-tested and working

@cameronrulten Good question on the testing. I do test all of the pull requests, and our demo branch where these features are drafted has also been used and tested by us over the last few months. Right now, the tests are done by hand, unfortunately. I re-run a number of different flag combinations to compare to main using fitsdiff, that way all differences (if any) in output are accounted for. We have a plan to set up CI for automated v2dl3-vegas testing soon.

[GernotMaier]

All fine with me, thanks!