docs: public static Element drawCross(SVGPlot svgp, Projection2D proj, NumberVector mid, double radius) {
      final double[] v_mid = mid.toArray();
      final long[] dims = proj.getVisibleDimensions2D();
  
      SVGPath path = new SVGPath();
      for(int dim = BitsUtil.nextSetBit(dims, 0); dim >= 0; dim = BitsUtil.nextSetBit(dims, dim + 1)) {
        v_mid[dim] += radius;
        double[] p1 = proj.fastProjectDataToRenderSpace(v_mid);
        v_mid[dim] -= radius * 2;
        double[] p2 = proj.fastProjectDataToRenderSpace(v_mid);
        v_mid[dim] += radius;
        path.moveTo(p1[0], p1[1]).drawTo(p2[0], p2[1]).close();
      }
      return path.makeElement(svgp);
    }