in classes/privacy/provider.php [155:169]
public static function delete_submission_for_userid(assign_plugin_request_data $deletedata) {
global $DB;
$assignmentid = $deletedata->get_assign()->get_instance()->id;
$submissionid = $deletedata->get_pluginobject()->id;
// Delete files.
$fs = get_file_storage();
$fs->delete_area_files($deletedata->get_context()->id, 'assignsubmission_onenote',
\local_onenote\api\base::ASSIGNSUBMISSION_ONENOTE_FILEAREA, $submissionid);
// Delete the records in the table.
$filters = ['assignment' => $assignmentid, 'submission' => $submissionid];
$DB->delete_records('assignsubmission_onenote', $filters);
}