test1/public/drupal-8.3.1/modules/user_import/user_import....

<?php

function user_import_theme(/*$existing, $type, $theme, $path*/) {
    return array(
        'custom_form' => array(
            'variables' => ['ldapAccounts' => NULL, 'newAccounts' => NULL, 'myForm' => NULL],
            'render element' => 'form',
            'path' => 'modules/user_import/templates',
            'template' => 'user_import_page',
        ),
    );
}