anchor.diff:  import 'package:flutter/foundation.dart';
   import 'package:flutter/gestures.dart';
   import 'package:flutter/rendering.dart';
  +import 'package:flutter/services.dart';
   
   import 'bar_chart_painter.dart';
   
  
positive.code:   }
  
    BarTouchCallback? _touchCallback;
    set touchCallback(BarTouchCallback? value) {
      _touchCallback = value;
    }
  
negative.code: 
    BarChartData get data => _data;
    BarChartData _data;
  
    set data(BarChartData value) {
      if (_data == value) return;
      _data = value;
  