@Override
 public OutputT extractOutput(
     K key,
     AccumT accumulator,
     PipelineOptions options,
     SideInputReader sideInputReader,
     Collection<? extends BoundedWindow> windows) {
   return keyedCombineFn.extractOutput(key, accumulator);
 }
 @Override
 public OutputT extractOutput(K key, AccumT accumulator, OldDoFn<?, ?>.ProcessContext c) {
   return keyedCombineFn.extractOutput(key, accumulator);
 }