message: Fix bug with sorting columns in group by using time shift
diff: @@ -1149,7 +1149,7 @@ class NVD3TimeSeriesViz(NVD3Viz):
  if self._extra_chart_data:
  chart_data += self._extra_chart_data
  - chart_data = sorted(chart_data, key=lambda x: x['key'])
  + chart_data = sorted(chart_data, key=lambda x: tuple(x['key']))
  return chart_data
  