Adoption of Final Qualifier in SymPy Classes

[sylee957]

I don't think that this may need separate SymPEP because it is highly relevant with
#4,
but this was originally asked for,
and I'm trying to add this because we may align with Python PEPs one-to-one.

[moorepants]

Is this proposal to request a general permission to use the @final decorator? Or is it about wanting to add that decorator to some specific existing methods in SymPy's (core) classes?

[asmeurer]

Is there a way to override the final decorator if you know what you are doing?

[sylee957]

you can always silence the type checker

[oscarbenjamin]

Is there a way to override the final decorator

The decorator has no runtime effect. You can still subclass a class that is marked as final but editors, typecheckers etc would warn about it.

If someone would like to do it anyway but wants to use e.g. mypy then they would need to add type: ignore to silence the type checker.