Add API for updating the signup status

I am trying to update the singnup_pay module to Drupal 6. I am at the point where the singup_pay module is supposed to update the status of the signup after PayPal's IPN has responded successfully. At line 648 of signup_pay.module, I see the code that will interface with a signup_status 5.x function called signup_status_operations().

if (module_exists('signup_status')) {
	$user = (int)$custom['uid'] ? (int)$custom['uid'] : (int)$custom['uid'].":".$mail;
	$users = array($user);
	$new_code = variable_get(SIGNUP_PAY_PAID_STATUS_CODE, SIGNUP_PAY_DEFAULT_PAID_STATUS_CODE);
	signup_status_operations($users, $custom['nid'], 'status_code', $new_code);
}

This function does not exist in the 6.x version of signup_status(). Where did it go? Is there a new API that should be used?

Signup_pay has awareness of signup_status which allows us to setup a "paid status code" in the signup_pay configuration screen (admin/settings/signup_pay). This allows us me to select a status to change the signup to when returning from PayPal: "Select the status code which will be used when a payment transaction is completed successfully. Note that you can also insert your own status code, such as "Paid"."

Thanks!