That is exactly what the second script from the repository article does. You need to specify the distinguished name (DN) of the group in the $groupDNs variable. The script will return true if the user is a member of the group itself or any of its nested groups.
If you need to check membership of only one group, you can use the built-in condition If is a member of <Group>. To check membership in nested groups, make sure the Check direct members only option is not enabled.