class VarianceFn extends Combine.CombineFn<T, VarianceAccumulator, T> {

  @Override
  public Coder<VarianceAccumulator> getAccumulatorCoder(
      CoderRegistry registry, Coder<T> inputCoder) {
    return SerializableCoder.of(VarianceAccumulator.class);
  }

  private  VarianceFn(boolean isSample, SerializableFunction<BigDecimal, T> decimalConverter);

}