in classes/privacy/provider.php [134:143]
public static function delete_submission_for_context(assign_plugin_request_data $requestdata) {
global $DB;
$fs = get_file_storage();
$fs->delete_area_files($requestdata->get_context()->id, 'assignsubmission_onenote',
\local_onenote\api\base::ASSIGNSUBMISSION_ONENOTE_FILEAREA);
$filters = ['assignment' => $requestdata->get_assign()->get_instance()->id];
$DB->delete_records('assignsubmission_onenote', $filters);
}