fix drawing legend for training history histograms
fix drawing legend for training history histograms

karies/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,karies/root,karies/root,olifre/root,olifre/root,karies/root,olifre/root,karies/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,karies/root