python 递归遍历文件夹得到json格式目录树目录结构,输出的json目录结构如下:[{"title":"file1","value":"file"},{"title":"general","value":"dir","subdir":[{"title":"file2","value":"file"},{"title":"photo","value":"dir","subdir":[{"title":"file4","value":"file"},{"title":"file3","valu