code: protected UploadPartRequest newUploadPartRequest(PartCreationEvent event,
              final File part) {
          final UploadPartRequest reqUploadPart = new UploadPartRequest()
              .withBucketName(req.getBucketName())
              .withFile(part)
              .withKey(req.getKey())
              .withPartNumber(event.getPartNumber())
              .withPartSize(part.length())
              .withLastPart(event.isLastPart())
              .withUploadId(uploadId)
              .withObjectMetadata(req.getUploadPartMetadata())
              ;
          return reqUploadPart;
      }
docs: Creates and returns an upload-part request corresponding to a ciphertext
  file upon a part-creation event.
  
  @param event
  the part-creation event of the ciphertxt file.
  @param part
  the created ciphertext file corresponding to the upload-part