code: def upload_files(tree, file_diff):
      
      # Upload new files to CC
      config.LOGGER.info("\nUploading {0} new file(s) to Kolibri Studio...".format(len(file_diff)))
      tree.upload_files(file_diff)
      tree.reattempt_upload_fails()
      return file_diff
docs: upload_files: Upload files to Kolibri Studio
          Args:
              tree (ChannelManager): manager to handle communication to Kolibri Studio
              file_diff ([str]): list of files to upload
          Returns: None