矩形树图 itemStyle 无效echarts treemap配置项内容和展示

series.itemStyle 设置无效，data.itemStyle 设置有效

      option = {
    title: {
        text: '矩形树图 itemStyle 无效'
    },
    series: [{
        type: 'treemap',
        data: [{
            name: 'nodeA',
            value: 10,
            children: [{
                name: 'nodeAa',
                value: 4
            }, {
                name: 'nodeAb',
                value: 6
            }],
            itemStyle: {
                normal: {
                    color: 'green'
                }
            }
        }, {
            name: 'nodeB',
            value: 20,
            children: [{
                name: 'nodeBa',
                value: 20,
                children: [{
                    name: 'nodeBa1',
                    value: 20
                }]
            }]
        }],
        
        // 无效
        itemStyle: {
            normal: {
                color: 'blue'
            }
        }
    }]
};