@Override
  public void reset() {
    for (int i=0; i< numBitVectors; i++) {
      bitVector[i].clear();
    }
  }
Resets a distinctValueEstimator object to its original state.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/common/ndv/fm/FMSketch.java