Add support for PEP 661 sentinels #591
Description
We should add a PEP 661-style Sentinel class; see https://discuss.python.org/t/pep-661-sentinel-values/9126/243
(For clarity: I won't work on this myself but I'll review a PR.)
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We should add a PEP 661-style Sentinel class; see https://discuss.python.org/t/pep-661-sentinel-values/9126/243
(For clarity: I won't work on this myself but I'll review a PR.)