public function initiateMultipartUpload(
        $bucketName,
        $key,
        $options = array()
    ) {
        list($config, $storageClass) = $this->parseOptions(
            $options, 
            BosOptions::CONFIG,
            BosOptions::STORAGE_CLASS);

        $headers = array(
            HttpHeaders::CONTENT_TYPE => HttpContentTypes::OCTET_STREAM,
        );
        if ($storageClass !== null) {
            $headers[HttpHeaders::BCE_STORAGE_CLASS] = $storageClass;
        } else {
            $headers[HttpHeaders::BCE_STORAGE_CLASS] = StorageClass::STANDARD;
        }

        return $this->sendRequest(
            HttpMethod::POST,
            array(
                BosOptions::CONFIG => $config,
                'bucket_name' => $bucketName,
                'key' => $key,
                'headers' => $headers,
                'params' => array('uploads' => ''),
            )
        );
    }