docs: public static double[] centroid(SpatialComparable obj) {
      final int dim = obj.getDimensionality();
      double[] centroid = new double[dim];
      for(int d = 0; d < dim; d++) {
        centroid[d] = (obj.getMax(d) + obj.getMin(d)) * .5;
      }
      return centroid;
    }