Basic: how to extend and namespace Page.php

Questions
1

Silverstripe Version: 5.4

Question:

I am trying to upgrade a very old site. Probably started as Silverstripe 2.0 and is now SS3.1.9. I get things should namespaced. However, if I namespace Page.php, I get into problems. What is the right way of handling/namespacing Page.php and its controller?

// Include any relevant code. If you have a lot of code, link to a gist instead.
2

You do not need to namespace page or the page controller

<?php
use SilverStripe\CMS\Model\SiteTree;
class Page extends SiteTree
{

Then in other page types

use Page;
3

Do I need a backslash? use \Page;?

4

You don’t even need that: the default namespace is always visible.