Find subscriber and delete subscription

<?php

global $Db, $Subscriber, $SubscribersList;

//Find a subscriber via email
$Db -> model = $Subscriber -> model;
$email = 'email@domain.com'; //A valid email address
$subscriber = $Db -> find(array('email' => $email));

//Remove a subscription
$Db -> model = $SubscribersList -> model;
$subscriber_id = $subscriber -> id; //from above $subscriber object
$list_id = '3'; //The ID of the mailing list subscribed to
$Db -> delete_all(array('subscriber_id' => $subscriber_id, 'list_id' => $list_id));

?>