new ref impl

Author: JelleZijlstra

peps/pep-0661.rst

@@ -272,10 +272,9 @@ This proposal should have no security implications.
 Reference Implementation
 ========================
 
-A previous reference implementation is found in a dedicated GitHub repo [7]_.
-Following the Steering Council's feedback, the implementation should be
-simplified before being proposed for CPython.  A sketch of the intended
-behavior follows::
+A reference implementation is available as a CPython pull request [10]_.  A
+previous reference implementation is found in a dedicated GitHub repo [7]_.
+A sketch of the intended behavior follows::
 
     class sentinel:
         """Unique sentinel values."""
@@ -547,6 +546,7 @@ Footnotes
 .. [7] `Reference implementation at the taleinat/python-stdlib-sentinels GitHub repo <https://github.com/taleinat/python-stdlib-sentinels>`_
 .. [8] `bpo-35712: Make NotImplemented unusable in boolean context <https://github.com/python/cpython/issues/79893>`_
 .. [9] `Discussion thread about type signatures for these sentinels on the typing-sig mailing list <https://mail.python.org/archives/list/typing-sig@python.org/thread/NDEJ7UCDPINP634GXWDARVMTGDVSNBKV/#LVCPTY26JQJW7NKGKGAZXHQKWVW7GOGL>`_
+.. [10] `CPython reference implementation <https://github.com/JelleZijlstra/cpython/pull/4>`_
 
 
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