What is in a laravel application Menu::render(), Assets::render(), Notify::render()?

I'm working on a laravel app that I haven't coded. I need to do some modifications and in my blade templates I see some code like this:

 {!! Menu::render('client', 1, 1) !!}

{!! Assets::renderCss() !!}

{!! Notify::render() !!}
{!! Assets::renderJs() !!}

I understand that it used to link some code like stylesheet, script js or menu but I can't find these functions. I search a little in the laravel documentation but no results. Is there some customs functions from my app? The development environment is not very convenient and I can't make search into the whole files... I wanted to modify the related menu and I didn't find the files where I have to modify. Forgive me if my question is silly but I'm starting in development...

Thanks for your answers

via Chebli Mohamed