code: def _delegate(self, path):
          # type: (Text) -> Tuple[FS, Text]
          
          _path = forcedir(abspath(normpath(path)))
          is_mounted = _path.startswith
  
          for mount_path, fs in self.mounts:
              if is_mounted(mount_path):
                  return fs, _path[len(mount_path) :].rstrip("/")
  
          return self.default_fs, path
docs: Get the delegate FS for a given path.
  
          Arguments:
              path (str): A path.
  
          Returns:
              (FS, str): a tuple of ``(<fs>, <path>)`` for a mounted filesystem,
              or ``(None, None)`` if no filesystem is mounted on the
              given ``path``.