root/devel/mod/profile/lib/groups_delete.php

<?php
global $USER;

    // groups:delete
    // When an access group is deleted, revert all profile items restricted to that group to private

        if (isset($parameter) && logged_on) {
            
            // Grab group ID
                $group_id = (int) $parameter;
            // Create 'private' access string for current user
                $access = "user" . $_SESSION['userid'];
                
            // Update profile_data table, setting access to $access 
            // where the owner is the current user and access = 'group$group_id'
                set_field('profile_data','access',$access,'access','group'.$group_id,'owner',$USER->ident);

        }

?>