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:   /// [ProgressIndicatorThemeData.color] will be used. If that
    /// is null then the current theme's [ColorScheme.primary] will
    /// be used by default.
    ///
    /// This property is ignored if used in an adaptive constructor inside an iOS
    /// environment.
    /// {@endtemplate}
    final Color? color;
  
  
negative.code:   /// If null, the progress indicator is rendered with [color]. If that is null,
    /// then it will use the ambient [ProgressIndicatorThemeData.color]. If that
    /// is also null then it defaults to the current theme's [ColorScheme.primary].
    final Animation<Color?>? valueColor;
  
    /// {@template flutter.progress_indicator.ProgressIndicator.semanticsLabel}
  