def upload_files(tree, file_diff):
    """ 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
    """
    # 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
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