code: function () {
      // There is a possibility that the incoming stream was empty, therefore the MPU never started
      // and cannot be finalized.
      if (multipartUploadID) {
        cachedClient.completeMultipartUpload(
          {
            Bucket: destinationDetails.Bucket,
            Key: destinationDetails.Key,
            UploadId: multipartUploadID,
            MultipartUpload: {
              Parts: partIds
            }
          },
          function (err, result) {
            if (err)
              abortUpload('Failed to complete the multipart upload on S3: ' + JSON.stringify(err));
            else {
              // Emit both events for backwards compatibility, and to follow the spec.
              ws.emit('uploaded', result);
              ws.emit('finish', result);
              started = false;
            }
          }
        );
      }
    }
docs: Turn all the individual parts we uploaded to S3 into a finalized upload.