Pass variable as final

Proposal:
The idea is to be able to pass variables as constants, mimicking c++ or rust behaviour such as. And have this be solely as part of the typings ecosystem. It's extremely helpful when reviewing code, or starting to use new codebases.

Issue opened in cpython repo: #113654

fn my_function(mut changeable: &String, unchangeable: &String) {}

In python I suggest the following:

def my_function(changeable: str, unchangeable: Final[str])-> None:
    arguments_that_changes += "world!"
    return arguments_that_changes + argument_that_stays_constant

Start by reading the linked CPython issue #113654 and reviewing how Final is currently used in Python typing. The proposal needs a settled specification for parameter annotations and an agreed typing-ecosystem change before implementation can be scoped; done would require an accepted design and corresponding repository updates.