public static function get_instance()
 {
     if (self::$instance === null) {
         self::$instance = new self();
     }
     return self::$instance;
 }
<?php

/*
 * Autoloader
 */
require_once TYPES_ABSPATH . '/library/toolset/autoloader/autoloader.php';
$autoloader = Toolset_Autoloader::get_instance();
$autoloader->add_paths('Types', array(TYPES_ABSPATH . '/application/controllers', TYPES_ABSPATH . '/application/models'));
$autoloader->add_path('Toolset', TYPES_ABSPATH . '/library/toolset');
/*
 * Load old Types
 */
if (!defined('WPCF_RELPATH')) {
    define('WPCF_RELPATH', TYPES_RELPATH . '/library/toolset/types');
}
if (!defined('WPCF_EMBEDDED_TOOLSET_ABSPATH')) {
    define('WPCF_EMBEDDED_TOOLSET_ABSPATH', TYPES_ABSPATH . '/library/toolset');
}
if (!defined('WPCF_EMBEDDED_TOOLSET_RELPATH')) {
    define('WPCF_EMBEDDED_TOOLSET_RELPATH', TYPES_RELPATH . '/library/toolset');
}
if (!defined('WPTOOLSET_COMMON_PATH')) {
    define('WPTOOLSET_COMMON_PATH', TYPES_ABSPATH . '/library/toolset/toolset-common');
}
if (!defined('EDITOR_ADDON_RELPATH')) {
    define('EDITOR_ADDON_RELPATH', WPCF_EMBEDDED_TOOLSET_RELPATH . '/toolset-common/visual-editor');
}
// installer
$installer = TYPES_ABSPATH . '/library/otgs/installer/loader.php';
if (file_exists($installer)) {
    /** @noinspection PhpIncludeInspection */