code: function stat(path, callback) {
          appshell.fs.stat(path, function (err, stats) {
              if (err) {
                  callback(_mapError(err));
              } else {
                  var options = {
                      isFile: stats.isFile(),
                      mtime: stats.mtime,
                      size: stats.size,
                      realPath: stats.realPath,
                      hash: stats.mtime.getTime()
                  };
  
                  var fsStats = new FileSystemStats(options);
  
                  callback(null, fsStats);
              }
          });
      }
docs: Stat the file or directory at the given path, calling back
  asynchronously with either a FileSystemError string or the entry's
  associated FileSystemStats object.
  
  @param {string} path
  @param {function(?string, FileSystemStats=)} callback