anchor.diff:  /// [LineChart] draws some [VerticalLine] (set by [LineChartData.extraLinesData]),
   /// in below or above of everything, it draws from bottom to top side of the chart.
   class VerticalLine extends FlLine {
  -
     /// Draws from bottom to top of the chart using the [x] value.
     final double x;
   
  
positive.code: 
  /// Draws a title on the [HorizontalLine]
  class HorizontalLineLabel extends FlLineLabel {
  
    /// Resolves a label for showing.
    final String Function(HorizontalLine) labelResolver;
  
  
negative.code: 
  /// Holds data for drawing line on the spots under the [BarAreaData].
  class BarAreaSpotsLine {
    /// Determines to show or hide all the lines.
    final bool show;
  
  