如何制作highcharts气泡图泡沫看起来像甜甜圈符号而不是完整的圆形圆圈？

Question

我有一个基本的highcharts气泡图。所有气泡都是圆形的cirlce。我想让它看起来像一个甜甜圈符号。我怎么能在Highcharts中做到这一点？

JSFiddle：http://jsfiddle.net/gh/get/jquery/1.9.1/highslide-software/highcharts.com/tree/master/samples/highcharts/demo/bubble/

代码

$(function () {
    $('#container').highcharts({

        chart: {
            type: 'bubble',
            zoomType: 'xy'
        },

        title: {
            text: 'Highcharts Bubbles'
        },

        series: [{
            data: [[97, 36, 79], [94, 74, 60], [68, 76, 58], [64, 87, 56], [68, 27, 73], [74, 99, 42], [7, 93, 87], [51, 69, 40], [38, 23, 33], [57, 86, 31]]
        }, {
            data: [[25, 10, 87], [2, 75, 59], [11, 54, 8], [86, 55, 93], [5, 3, 58], [90, 63, 44], [91, 33, 17], [97, 3, 56], [15, 67, 48], [54, 25, 81]]
        }, {
            data: [[47, 47, 21], [20, 12, 4], [6, 76, 91], [38, 30, 60], [57, 98, 64], [61, 17, 80], [83, 60, 13], [67, 78, 75], [64, 12, 10], [30, 77, 82]]
        }]
    });
});