private function doPermanentFetchToStream ($mediaID, $into)
    {
        $body = $this->client->send(
            new Request(
                'POST',
                'https://api.weixin.qq.com/cgi-bin/material/get_material',
                [],
                json_encode([
                    'media_id' => $mediaID,
                ])
            ),
            [
                RequestOptions::SINK => $this->createWritableStream($into),
            ]
        )->getBody();

        if ($body->isSeekable()) {
            $body->seek(0);
        }

        return $body->detach();
    }