code: def _handle_browse(self, relpath, params):
      
      abspath = os.path.normpath(os.path.join(self._root, relpath))
      if not abspath.startswith(self._root):
        raise ValueError  # Prevent using .. to get files from anywhere other than root.
      if os.path.isdir(abspath):
        self._serve_dir(abspath, params)
      elif os.path.isfile(abspath):
        self._serve_file(abspath, params)
docs: Handle requests to browse the filesystem under the build root.