code: def last_updated(self, subpath=None):
          
          try:
              return os.path.getmtime(self.readme_for(subpath))
          except ReadmeNotFoundError:
              return None
          # OSError for Python 3 base class, EnvironmentError for Python 2
          except (OSError, EnvironmentError) as ex:
              if ex.errno == errno.ENOENT:
                  return None
              raise
docs: Returns the time of the last modification of the Readme or
          specified subpath, or None if the file does not exist.
  
          The return value is a number giving the number of seconds since
          the epoch (see the time module).
  
          Raises werkzeug.exceptions.NotFound if the resulting path
          would fall out of the root directory.