code: public BoxRequestsFile.UploadSessionPart getUploadSessionPartRequest(File file, BoxUploadSession uploadSession,
                                                                           int partNumber) throws IOException {
          return new BoxRequestsFile.UploadSessionPart(file, uploadSession, partNumber, mSession);
      }
docs: Get a request for uploading a part to a BoxUploadSession
  @param file the file that is used to read the chunk using the ranges for the partnumber
  @param uploadSession the BoxUploadSession
  @param partNumber The part number being uploaded
  @return