Highcharts -如何在一个系列中获得堆栈的值

我想知道是否有可能在我的工具提示 Highcharts中使用一系列堆栈的值。

我使用this.series.stackKey得到它，就像下面的例子:

$(function () {
    $('#container').highcharts({
        chart: {
            type: 'column'
        },
        title: {
            text: 'Total fruit consumtion, grouped by gender'
        },
        xAxis: {
            categories: ['Apples', 'Oranges', 'Pears', 'Grapes', 'Bananas']
        },
        yAxis: {
            allowDecimals: false,
            min: 0,
            title: {
                text: 'Number of fruits'
            }
        },
        tooltip: {
            formatter: function () {
                return '<b>' + this.x + '</b><br/>' +
                    this.series.name + ': ' + this.y + '<br/>' +
                    'Total: ' + this.point.stackTotal + ' Stack: ' + this.series.stackKey;
            }
        },
        plotOptions: {
            column: {
                stacking: 'normal'
            }
        },
        series: [{
            name: 'John',
            data: [5, 3, 4, 7, 2],
            stack: 'male'
        }, {
            name: 'Joe',
            data: [3, 4, 4, 2, 5],
            stack: 'male'
        }, {
            name: 'Jane',
            data: [2, 5, 6, 2, 1],
            stack: 'female'
        }, {
            name: 'Janet',
            data: [3, 0, 4, 4, 3],
            stack: 'female'
        }]
    });
});

但是工具提示显示了像"columnfemale"这样的东西，我只想看到堆栈值:"female" .

小提琴:http://jsfiddle.net/5nLa3saf/