code: public BoxRequestsFile.UploadSessionPart getUploadSessionPartRequest(InputStream is, long fileSize, BoxUploadSession uploadSession,
                                                                           int partNumber) throws IOException {
          return new BoxRequestsFile.UploadSessionPart(is, fileSize, uploadSession, partNumber, mSession);
      }
docs: Get a request for uploading a part to a BoxUploadSession
  @param is File InputStream to get read
  @param fileSize File size
  @param uploadSession the multipart upload session (BoxUploadSession)
  @param partNumber The part number being uploaded
  @return the UploadSessionPart object
  @throws IOException