use only TGraphs
Change to write only TGraphs instead of TMultiGraphs and TCanvases to enable superimposing plots, e.g. as in: https://lblhcbpr.cern.ch/#/app/rootfileviewer?apps=5&withNightly=false&checkSpecific=false&nightlyVersionNumber=10&jobs=61872&jobs=61883 FYI @dovombru @sstahl
Edited by Maciej Pawel Szymanski