What namespace is valid for xml attributes inside svg?

Question

JavaScript

The task is to start the svg animation through js. My (not) implementation - create a dom node with the animate tag, set the necessary attributes, insert it at the end of the svg. The problem is when doing

elem.setAttributeNS('http://www.w3.org/2000/xmlns', 'xmlns:xlink', 'http://www.w3.org/1999/xlink')

(as well as similarly setting any other attribute) I catch the error:

Uncaught DOMException: Failed to execute 'setAttributeNS' on 'Element': ' www.w3.org/2000/xmlns ' is an invalid namespace for attributes.

If you try to use ordinary .setAttribute()and .createElement(), then the animation simply does not work without any errors.
Question: what namespace is valid for xml attributes inside svg?
Look at the situation (see the error in the console)

Answer 1

Or something like this:
https://codepen.io/elijah_tr/pen/pLqYLp
(probably not cross-browser)