: api.visual('color'),
                        fill: null
                    });

                    return {
                        type: 'group',
                        children: [{
                            type: 'line',
                            shape: {
                                x1: highPoint[0] - halfWidth, y1: highPoint[1],
                                x2: highPoint[0] + halfWidth, y2: highPoint[1]
                            },
                            style: style
              