docs: public Confusion getConfusionMatrixAtThreshold(double threshold) {
          Point p = getPointAtThreshold(threshold);
          int idx = p.idx;
          int tn = totalCount - (tpCount[idx] + fpCount[idx] + fnCount[idx]);
          return new Confusion(p, tpCount[idx], fpCount[idx], fnCount[idx], tn);
      }