anchor.diff:  import 'dart:async';
   import 'dart:html';
  +import 'dart:math' as math;
   import 'dart:svg' as svg;
   import 'dart:convert' show JSON;
   
   import 'package:svg_pan_zoom/svg_pan_zoom.dart' as panzoom;
  +
  +panzoom.SvgPanZoom panZoom;
  +String visSelector = '.inner';
  +int visWidth = 1000;
  +int visHeight = 500;
   
   void main() {
     querySelector('#path-to-json').onKeyUp.listen(pathToJsonHander);
  
positive.code:   group.nodes.insert(0, rect);
  
    // Adjust the viewport on the parent svg element.
    innerSvg.viewport.width = (maxX - minX).toInt();
    innerSvg.viewport.height = (maxY - minY).toInt();
  }
  
  Future prettyString(Map map) async {
  
negative.code: }
  
  void displayData(List data) {
    // Before doing anything else, reset the viewport of the visualisation.
    resetVisualisation();
    svg.SvgSvgElement innerSvg = querySelector('.inner-svg');
    svg.GElement group = innerSvg.querySelector('#viewport');
    group.nodes.clear();
  