public function paginateUsers ($nextOpenID = null)
    {
        $json = json_decode(
            $this->client->send(
                new Request(
                    'GET',
                    Uri::withQueryValue(new Uri('https://api.weixin.qq.com/cgi-bin/user/get'), 'next_openid',
                        $nextOpenID)
                )
            )->getBody()
        );

        if (! isset($json->total)) {
            return new PaginatedResultSet(null, 0, []);
        } elseif (! isset($json->next_openid, $json->data->openid)) {
            return new PaginatedResultSet(null, $json->total, []);
        } else {
            return new PaginatedResultSet($json->next_openid ?: null, $json->total, $json->data->openid);
        }
    }