code: def _multi_permission_mask(mode):
      
      def compose(f, g):
          return lambda *args, **kwargs: g(f(*args, **kwargs))
      return functools.reduce(compose, map(_permission_mask, mode.split(',')))
docs: Support multiple, comma-separated Unix chmod symbolic modes.
  
      >>> _multi_permission_mask('a=r,u+w')(0) == 0o644
      True