[issue43923] Can't create generic NamedTuple as of py3.9

[Steven Silvester]

Steven Silvester <steven.silvester at gmail.com> added the comment:

The use case that prompted https://github.com/python/cpython/pull/31679 is that we are adding typings to `PyMongo`.  We are late to using typings,  because we only recently dropped Python 2.7 support.  

We have an existing options class that subclasses `NamedTuple`.  We would like to make that class `Generic`, but are currently blocked.  

Our current workaround is to create a separate stub file that uses `class CodecOptions(Tuple, Generic[T])` and explicitly re-declares the `NamedTuple` API.

Switching to `dataclass` would be disruptive, since we still support Python 3.6 and only rely on the standard library.  We would also require a major version update since it would be an API change.

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nosy: +Steven Silvester

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