code: function(workspace) {
      var containerBlock = workspace.newBlock('lists_create_with_container');
      containerBlock.initSvg();
      var connection = containerBlock.getInput('STACK').connection;
      for (var i = 0; i < this.itemCount_; i++) {
        var itemBlock = workspace.newBlock('lists_create_with_item');
        itemBlock.initSvg();
        connection.connect(itemBlock.previousConnection);
        connection = itemBlock.nextConnection;
      }
      return containerBlock;
    }
docs: Populate the mutator's dialog with this block's components.
  @param {!Blockly.Workspace} workspace Mutator's workspace.
  @return {!Blockly.Block} Root block in mutator.
  @this Blockly.Block