code: function _getSelectedCfg(type, cfg) {
    var geom = cfg.geom;
    var coord = geom.get('coord');
    var point = cfg.point;
    var r = 7.5;
    var selectedCfg = void 0;
    if (coord && coord.type === 'theta') {
      var thetaCfg = getThetaCfg(point, coord);
      var middleAngle = (thetaCfg.endAngle - thetaCfg.startAngle) / 2 + thetaCfg.startAngle;
      var x = r * Math.cos(middleAngle);
      var y = r * Math.sin(middleAngle);
      selectedCfg = {
        transform: [['t', x, y]]
      };
    }
    return Util.mix({}, selectedCfg);
  }
docs: 获取选中时的样式，当前仅支持饼图