add flag for run3
This MR introduces a flag for Run-3 data and mc21, so that it becomes possible to condition trainings on the relevant datasets in case that mc20 and mc21 data is combined for algorithm training.
This MR introduces a flag for Run-3 data and mc21, so that it becomes possible to condition trainings on the relevant datasets in case that mc20 and mc21 data is combined for algorithm training.