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

  @Override
  public VarianceAccumulator addInput(VarianceAccumulator currentVariance, T rawInput) {

    if (rawInput == null) {
      return currentVariance;
    }

    return currentVariance.combineWith(
        VarianceAccumulator.ofSingleElement(SqlFunctions.toBigDecimal(rawInput)));
  }

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

}