Combine 'categories'
Rather common use case: plots are made for a number of categories (e.g. dilepton mass for elel, mumu and mixed), but for presentations a combined plot is used (summing the category histograms).
The CommonTools/Factories inserted runtime checks whether a lepton is an electron or muon all over the place, it seems easier to fill only the per-category histograms and sum them in plotIt (needs changes there, but it could be done in a backwards compatible way by adding a 'histograms' key to the plot config, with the list of histogram names to sum for the plot).
On the python side we could ask for a separate list of plots (without 'result' from the RDataFrame, but still added to the plotIt config), e.g. CombinedPlot(list-of-category-plots)
- to be tried.