in classes/privacy/provider.php [137:149]
public static function delete_feedback_for_grade(assign_plugin_request_data $requestdata) {
global $DB;
$fs = new \file_storage();
$fs->delete_area_files($requestdata->get_context()->id, 'assignfeedback_onenote',
\local_onenote\api\base::ASSIGNFEEDBACK_ONENOTE_FILEAREA, $requestdata->get_pluginobject()->id);
$filters = [
'assignment' => $requestdata->get_assign()->get_instance()->id,
'grade' => $requestdata->get_pluginobject()->id
];
$DB->delete_records('assignfeedback_onenote', $filters);
}