docs: def _effective_perm_list_from_iter(self, perm_iter):
          """Return list of effective permissions for for highest permission in
          ``perm_iter``, ordered lower to higher, or None if ``perm_iter`` is empty."""
          highest_perm_str = self._highest_perm_from_iter(perm_iter)
          return (
              self._equal_or_lower_perm_list(highest_perm_str)
              if highest_perm_str is not None
              else None
          )