docs: def path_shift(self, shift=1):
          """ Shift path segments from :attr:`path` to :attr:`script_name` and
              vice versa.
  
             :param shift: The number of path segments to shift. May be negative
                           to change the shift direction. (default: 1)
          """
          script, path = path_shift(self.environ.get('SCRIPT_NAME', '/'), self.path, shift)
          self['SCRIPT_NAME'], self['PATH_INFO'] = script, path