WordPressのプラグインで、get_template_part的なものを使いたい

<?php// wp-content/plugins/wp-onocom-plugin.php class wp_onocom_plugin { static $instance = null; function __construct(){ self::$instance = $this; } public static function get_instance() { if( self::$instance != null ) { return self::$instance; } else { return new self(); } } public function get_plugin_template_part($slug, $name = null) { $templates = array(); $name = (string) $name; if ( '' !== $name ) $templates[] = "{$slug}-{$name}.php"; $templates[] = "{$slug}.php"; $located = ''; foreach ( (array) $templates as $template_name ) { if ( !$template_name ) { continue; } if ( file_exists($this->get_plugin_path() . '/' . $template_name) ) { $located = $this->get_plugin_path() . '/' . $template_name; break; } } if($located) { require_once( $located ); } } public function get_plugin_url() { return plugins_url("",__FILE__); } public function get_plugin_path() { return dirname(__FILE__); }}