Gtk.IconFactory.prototype.lookup

function lookup(stock_id:String):Gtk.IconSet {
    // Gjs wrapper for gtk_icon_factory_lookup()
}

Looks up stock_id in the icon factory, returning an icon set if found, otherwise null. For display to the user, you should use Gtk.lookup_icon_set on the Gtk.Style for the widget that will display the icon, instead of using this function directly, so that themes are taken into account.