@Override
 public void populateDisplayData(DisplayData.Builder builder) {
   super.populateDisplayData(builder);
   CombineFns.populateDisplayData(builder, keyedCombineFns);
 }
 @Override
 public void populateDisplayData(DisplayData.Builder builder) {
   super.populateDisplayData(builder);
   CombineFns.populateDisplayData(builder, combineFnWithContexts);
 }