@final
@cache_readonly
def group_keys_seq(self):
    if (len(self.groupings) == 1):
        return self.levels[0]
    else:
        (ids, _, ngroups) = self.group_info
        return get_flattened_list(ids, ngroups, self.levels, self.codes)
@final
@cache_readonly
def group_keys_seq(self):
    if (len(self.groupings) == 1):
        return self.levels[0]
    else:
        (ids, _, ngroups) = self.group_info
        return get_flattened_list(ids, ngroups, self.levels, self.codes)