Traits - language feature

Example from PHP:

// The template
trait TSingleton
{
    private static $_instance = null; 
    private function __construct(){} // Must have private default constructor and be aware not to open it in the class
    public static function getInstance()
    {
        if (null === self::$_instance)
        {
            self::$_instance = new self();
        }
        return self::$_instance;
    }
}
class FrontController
{
    use TSingleton;
}
// Can also be used in already extended classes
class WebSite extends SomeClass
{
    use TSingleton;
}

Example from Jule:

trait Person {
    fn get_full_name(self): str
    fn get_age(self): byte
}

Languages with Traits include PHP, Jule