code: def frombase(path1, path2):
      # type: (Text, Text) -> Text
      
      if not isparent(path1, path2):
          raise ValueError("path1 must be a prefix of path2")
      return path2[len(path1) :]
docs: Get the final path of ``path2`` that isn't in ``path1``.
  
      Arguments:
          path1 (str): A PyFilesytem path.
          path2 (str): A PyFilesytem path.
  
      Returns:
          str: the final part of ``path2``.
  
      Example:
          >>> frombase('foo/bar/', 'foo/bar/baz/egg')
          'baz/egg'