How do I set a select value in materialize CSS? (NO JQUERY)

Question

I am trying to set the value of my dropdown select, but there frankly isn't much documentation on any of this stuff anywhere. This is about all you get: https://materializecss.com/select.html

I am trying to do it the non-jQuery way.

This is the code I have tried:

1.

let instance = M.FormSelect.getInstance(document.getElementById('ptType'));
instance.input = document.getElementById('3');

let instance = M.FormSelect.getInstance(document.getElementById('ptType'));
instance.input = '3'

let instance = M.FormSelect.getInstance(document.getElementById('ptType'));
instance.value = '3'
// this one changes the "internal value", but doesn't show it on the actual drop down.

I have searched many times for a solution and nothing has ever come up. Not sure if anyone on here would know. Please help!