function getPartCountFromMd5(objMD) {
    const md5 = objMD['content-md5'];
    if (md5.includes('-')) {
        return md5.split('-')[1];
    }
    return null;
}
Gets parts count if object was put with mpu
@param {object} objMD - object metadata
@return {(Integer|null)} - number of parts of mpu object or null