Fxing bug in label generation for multiple groupbys (#3594)
Fxing bug in label generation for multiple groupbys (#3594)


apache/incubator-superset,airbnb/caravel,apache/incubator-superset,dmigo/incubator-superset,airbnb/caravel,alanmcruickshank/superset-dev,airbnb/superset,airbnb/superset,zhouyao1994/incubator-superset,apache/incubator-superset,dmigo/incubator-superset,zhouyao1994/incubator-superset,alanmcruickshank/superset-dev,alanmcruickshank/superset-dev,timifasubaa/incubator-superset,apache/incubator-superset,apache/incubator-superset,alanmcruickshank/superset-dev,mistercrunch/panoramix,dmigo/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,zhouyao1994/incubator-superset,mistercrunch/panoramix,airbnb/superset,dmigo/incubator-superset,timifasubaa/incubator-superset,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,airbnb/superset,timifasubaa/incubator-superset,mistercrunch/panoramix,airbnb/caravel,mistercrunch/panoramix