public static KllHistogramEstimator getKllHistogramEstimator(byte[] buf, int start, int len) {
    return new KllHistogramEstimator(KllUtils.deserializeKll(buf, start, len));
  }
This function deserializes the serialized KLL histogram estimator from a byte array.
@param buf to deserialize
@param start start index for deserialization
@param len start+len is deserialized
@return KLL histogram estimator
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/common/histogram/KllHistogramEstimatorFactory.java