How to make a Twig extension call without parameters?

Question

Twig

<?php

namespace MDSClient\Twig\Extensions;


use Twig\TwigFunction;

class TwigRandomLink extends \Twig_Extension
{

    public function getFunctions()
    {
        return [
            new TwigFunction('displayAttributes', [$this->getRandomLink()])]
        ];
    }

    /**
     * Get rand link
     * @return string
     */
    public function getRandomLink(): string
    {