code: function(options) {
      var fieldName = 'LIST';
      if (this.isCollapsed()) {
        return;
      }
      var currentVarName = this.getField(fieldName).text_;
      if (!this.isInFlyout) {
        var variablesList = this.workspace.getVariablesOfType('list');
        for (var i = 0; i < variablesList.length; i++) {
          var varName = variablesList[i].name;
          if (varName == currentVarName) continue;
  
          var option = {enabled: true};
          option.text = varName;
  
          option.callback =
              Blockly.Constants.Data.VARIABLE_OPTION_CALLBACK_FACTORY(this,
                  variablesList[i].getId(), fieldName);
          options.push(option);
        }
      } else {
        var renameOption = {
          text: Blockly.Msg.RENAME_LIST,
          enabled: true,
          callback: Blockly.Constants.Data.RENAME_OPTION_CALLBACK_FACTORY(this,
              fieldName)
        };
        var deleteOption = {
          text: Blockly.Msg.DELETE_LIST.replace('%1', currentVarName),
          enabled: true,
          callback: Blockly.Constants.Data.DELETE_OPTION_CALLBACK_FACTORY(this,
              fieldName)
        };
        options.push(renameOption);
        options.push(deleteOption);
      }
    }
docs: Add context menu option to change the selected list.
  @param {!Array} options List of menu options to add to.
  @this Blockly.Block