21.6: LHEFilters updates
requested to merge atlas-physics/pmg/mcexperts/powheg-experts/athena:21.6-Updating-LHEFilters into 21.6
This MR adds a new LHE filter in MCJobOptionUtils, to select events with a certain number of final state quarks, possibly with a certain parent (e.g. to select Z->bb events among Z->jj).
NB: I'm doing the sweep to master manually (see !53970 (merged)), as there need to be some further modifications for python3
Edited by Timothee Theveneaux-Pelzer