Support generic for Basic

[sylee957]

References to other Issues or PRs

Fixes #25399

Brief description of what is fixed or changed

Other comments

It may also not be obvious whether super().__init_subclass__ should be put at the before or after,
so I'm picking to put before the _prepare_class_assumptions(cls) line

Release Notes

• core
  • Fixed issue of Basic not subclassable with Generic by multiple inheritance.

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• core
  • Fixed issue of Basic not subclassable with Generic by multiple inheritance. (#25557 by @sylee957)

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#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
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Fixes #25399

#### Brief description of what is fixed or changed



#### Other comments

It may also not be obvious whether `super().__init_subclass__` should be put at the before or after,
so I'm picking to put before the `_prepare_class_assumptions(cls)` line

#### Release Notes

<!-- BEGIN RELEASE NOTES -->
- core
  - Fixed issue of `Basic` not subclassable with `Generic` by multiple inheritance.
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[asmeurer]

Calling super on overridden methods is always a good idea, so I'm +1 to this. I also have no idea if it matters if it's called at the top or bottom of the method.