nextcloud/apps/contacts/ajax/chooseaddressbook.php

<?php
/**
 * Copyright (c) 2011 Thomas Tanghus <thomas@tanghus.net>
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */

 
OC_JSON::checkLoggedIn();
OC_JSON::checkAppEnabled('contacts');

$output = new OC_TEMPLATE("contacts", "part.chooseaddressbook");
$output -> printpage();