docs: public double[][] getMeans() {
      double[][] newmeans = new double[centroids.length][];
      for(int i = 0; i < centroids.length; i++) {
        if(sizes[i] == 0) {
          newmeans[i] = means[i]; // Keep old mean.
          continue;
        }
        newmeans[i] = centroids[i];
      }
      return newmeans;
    }