PEP 749: Use __format__ instead of .format as param name

peps/pep-0749.rst

@@ -710,12 +710,14 @@ Signature of ``__annotate__`` functions
 
 However, using ``format`` as a parameter name could lead to collisions
 if an annotation uses a class named ``format``. The parameter should be
-positional-only and have a name that cannot be a legal identifier in order
-to avoid this problem.
-
-The current implementation uses the name ``.format`` with a leading
-dot, but the exact name should be considered an implementation detail
-and cannot be relied upon.
+positional-only and have a name that does not coincide with an
+identifier used by user code. We propose to use the name ``__format__``,
+as names with double underscores are reserved for the Python implementation.
+
+A previous version of this PEP proposed using the name ``.format`` with a
+leading dot. This has the advantage that it cannot collide with any
+identifier, reserved or not, but it also made it so ``inspect.signature``
+could not create a signature for annotate functions.
 
 The documentation may still use the name ``format`` for simplicity.