public function getRenderablesRecursively()
    {
        $renderables = [];
        foreach ($this->renderables as $renderable) {
            $renderables[] = $renderable;
            if ($renderable instanceof CompositeRenderableInterface) {
                $renderables = array_merge($renderables, $renderable->getRenderablesRecursively());
            }
        }
        return $renderables;
    }