code: function(nodes) {
                  var box = new kity.Box();
                  var i, node, matrix, contentBox;
                  for (i = 0; i < nodes.length; i++) {
                      node = nodes[i];
                      matrix = node.getLayoutTransform();
                      contentBox = node.getContentBox();
                      box = box.merge(matrix.transformBox(contentBox));
                  }
                  return box;
              }
docs: 工具方法：获取给点的节点所占的布局区域
  
  @param  {MinderNode[]} nodes 需要计算的节点
  
  @return {Box} 计算结果