public static AdaptiveHyperLogLog merge(AdaptiveHyperLogLog first, AdaptiveHyperLogLog second) {
   return new AdaptiveHyperLogLog(HyperLogLogUtil.mergeBuckets(first.buckets(), second.buckets()));
 }
 public void merge(AdaptiveHyperLogLog other) {
   estimator = makeEstimator(HyperLogLogUtil.mergeBuckets(this.buckets(), other.buckets()));
 }