get_sidebar( string $name = null )

function get_sidebar( $name = null ) {
	/**
	 * Fires before the sidebar template file is loaded.
	 *
	 * @since WP-2.2.0
	 * @since WP-2.8.0 $name parameter added.
	 *
	 * @param string|null $name Name of the specific sidebar file to use. null for the default sidebar.
	 */
	do_action( 'get_sidebar', $name );

	$templates = array();
	$name = (string) $name;
	if ( '' !== $name )
		$templates[] = "sidebar-{$name}.php";

	$templates[] = 'sidebar.php';

	locate_template( $templates, true );
}