anchor.diff:        },
   
         _setEditorToolbox: function () {
  -        const editor = $("mu-gobstones-custom-editor")[0];
  -
  -        // editor may have not yet been loaded
  -        // so there is nothing to do yet
  -        if (!editor) return;
  -
  -        editor.configureCustomToolboxFromUrl(this.toolboxUrl);
  +        const $editor = $("mu-gobstones-custom-editor")[0];
  +
  +        // there is no editor to configure
  +        if (!$editor) return;
  +
  +        $editor.configureCustomToolboxFromUrl(this.toolboxUrl);
         }
       });
     </script>
  
positive.code:       },
  
        _initializeBlocklyWorkspace() {
          this._setInitialXml();
          this._initializeWorkspace();
          this._subscribeToWorkspace(() => this._updateSolution());
  
negative.code:        * have no sense to have a toolboxUrl.
         */
        configureCustomToolboxFromUrl(toolboxUrl) {
          if (this.readOnly) return;
  
          console.debug('Configuring custom toolbox');
  
          $.get(toolboxUrl, (toolboxXml) => {
            this._initializeCustomToolboxBlocklyWorkspace(toolboxXml);
          });
        },
  
        /**
  