docs: function (dir) {
      let files = [];
      let list = fs.readdirSync(dir);
      list.forEach(function (file) {
          file = dir + '/' + file;
          let stat = fs.statSync(file);
          if (stat && stat.isDirectory()) files = files.concat(walk(file));
          else files.push(file);
      });
      return files;
  }