Changing Interface.function to Interface.purpose

[john-science]

What is the change? Why is it being made?

The name function in Interface.function clashes heavily with the Python reserved word "function". It is also just not a very helpful name, as it could mean almost anything.

close #2125

SCR Information

Change Type: trivial

One-Sentence Description: Changing Interface.function to Interface.purpose.

One-line Impact on Requirements: Minor edit to the implementation I_ARMI_INTERFACE on the requirement R_ARMI_INTERFACE

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify any new/changed code.
• The documentation is still up-to-date in the doc folder.
• The code style follows good practices.
• The dependencies are still up-to-date in pyproject.toml.

[john-science]

Do not merge this yet.

[drewj-tp]

LMK when this is ready for prime time 😸

[keckler]

This will break benchmarks

[john-science]

This will break benchmarks

We can talk offline, but I was expecting this to need a couple of small PRs downstream that I would make for everyone.

[john-science]

@keckler We should talk about your benchmark reactors. I would happily make (what I can only assume are very small changes) in your benchmark repos to help push this ARMI change through. Just give me a list of the affecting repos offline, and I can try to take it from there.