code: public Group init(final String priKey, final int count, final double estimate, final double ub,
        final double lb, final double fraction, final double rse) {
      this.count = count;
      est = estimate;
      this.ub = ub;
      this.lb = lb;
      this.fraction = fraction;
      this.rse = rse;
      this.priKey = priKey;
      return this;
    }
docs: Specifies the parameters to be listed as columns
  @param priKey the primary key of the FDT sketch
  @param count the number of retained rows associated with this group
  @param estimate the estimate of the original population associated with this group
  @param ub the upper bound of the estimate
  @param lb the lower bound of the extimate
  @param fraction the fraction of all retained rows of the sketch associated with this group
  @param rse the estimated Relative Standard Error for this group.
  @return return this