[issue36974] Implement PEP 590

[Jeroen Demeyer]

Change by Jeroen Demeyer <J.Demeyer at UGent.be>:


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pull_requests: +13733
pull_request: https://github.com/python/cpython/pull/13858

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue36974>
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