anchor.diff:    /// If null, this progress indicator is indeterminate, which means the
     /// indicator displays a predetermined animation that does not indicate how
     /// much actual progress is being made.
  -  ///
  -  /// This property is ignored if used in an adaptive constructor inside an iOS
  -  /// environment.
     final double? value;
   
     /// The progress indicator's background color.
  
positive.code:   /// If [CircularProgressIndicator.backgroundColor] is null then the
    /// ambient [ProgressIndicatorThemeData.circularTrackColor] will be used.
    /// If that is null, then the track will not be painted.
    ///
    /// This property is ignored if used in an adaptive constructor inside an iOS
    /// environment.
    /// {@endtemplate}
    @override
    Color? get backgroundColor => super.backgroundColor;
  
    /// The width of the line used to draw the circle.
    ///
    /// This property is ignored if used in an adaptive constructor inside an iOS
    /// environment.
    final double strokeWidth;
  
    @override
  
negative.code:   /// For determinate progress indicators, this will be defaulted to
    /// [ProgressIndicator.value] expressed as a percentage, i.e. `0.1` will
    /// become '10%'.
    /// {@endtemplate}
    final String? semanticsValue;
  
  