code: function getRangePath(points, smooth, isInCircle, cfg) {
    var topPoints = [];
    var isStack = cfg.isStack;
    var bottomPoints = [];
    for (var i = 0; i < points.length; i++) {
      var point = points[i];
      var tmp = ShapeUtil.splitPoints(point);
      bottomPoints.push(tmp[0]);
      topPoints.push(tmp[1]);
    }
    var topPath = getSinglePath(topPoints, smooth, isInCircle, cfg);
    var bottomPath = getSinglePath(bottomPoints, smooth, isInCircle, cfg);
    if (isStack) {
      return topPath;
    }
    return topPath.concat(bottomPath);
  }
docs: 获取带有上下区间的 path