metadataStorePart(mpuBucketName, partLocations,
                      metaStoreParams, log, cb) {
        assert.strictEqual(typeof mpuBucketName, 'string');
        const { partNumber, contentMD5, size, uploadId, lastModified, splitter, overheadField, ownerId }
            = metaStoreParams;
        const dateModified = typeof lastModified === 'string' ?
            lastModified : new Date().toJSON();
        assert.strictEqual(typeof splitter, 'string');
        const partKey = `${uploadId}${splitter}${partNumber}`;
        const omVal = {
            // Version 3 changes the format of partLocations
            // from an object to an array
            'md-model-version': 3,
            partLocations,
            'key': partKey,
            'last-modified': dateModified,
            'content-md5': contentMD5,
            'content-length': size,
            'owner-id': ownerId,
        };

        const params = {};
        if (overheadField) {
            params.overheadField = overheadField;
        }

        metadata.putObjectMD(mpuBucketName, partKey, omVal, params, log, err => {
            if (err) {
                log.error('error from metadata', { error: err });
                return cb(err);
            }
            return cb(null);
        });
    }
Stores metadata about a part of a multipart upload
@param {string} mpuBucketName - name of the special mpu bucket
@param {object []} partLocations - data retrieval info for part.
@param {string} partLocations[].key -
key in datastore for part
@param {string} partLocations[].dataStoreName - name of dataStore
@param {string} [partLocations[].size] - part size
@param {string} [partLocations[].sseCryptoScheme] - cryptoScheme
@param {string} [partLocations[].sseCipheredDataKey] - cipheredDataKey
@param {string} [partLocations[].sseAlgorithm] - encryption algo
@param {string} [partLocations[].masterKeyId] - masterKeyId
@param {object} metaStoreParams - custom built object
@param {object} log - request logger instance
@param {function} cb - callback to send error or move to next task
@return {undefined}