protected function unpublishedPhotos(array $sources)
    {
        $images = [];

        foreach ($sources as $index => $source) {
            $response = $this->fb
                ->post('/me/photos', [
                    'source' => new FacebookFile($source),
                    'published' => false,
                ])
                ->getDecodedBody();

            $images["attached_media[{$index}]"] = sprintf('{"media_fbid":"%d"}', $response['id']);
        }

        return $images;
    }