PEP 746: Apply comments from review (#3802)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

peps/pep-0746.rst

@@ -43,17 +43,23 @@ This use case comes up in libraries like :pypi:`pydantic`, which use
 
 Specification
 =============
-
-This PEP introduces a new ``__supports_type__`` protocol that both static and
-runtime type checkers can use to understand if a metadata object in
-``Annotated`` is valid for the given type. Objects that implement this protocol
-must have a method named ``__supports_type__`` that takes a single positional argument and
-returns ``bool``::
+This PEP introduces a protocol that can be used by static and runtime type checkers to validate
+the consistency between ``Annotated`` metadata and a given type.
+Objects that implement this protocol have a method named ``__supports_type__``
+that takes a single positional argument and returns ``bool``::
 
     class Int64:
         def __supports_type__(self, obj: int) -> bool:
             return isinstance(obj, int)
 
+The protocol being introduced would be defined as follows if it were to be defined in code form::
+
+    from typing import Protocol
+
+    class SupportsType[T](Protocol):
+        def __supports_type__(self, obj: T, /) -> bool:
+            ...
+
 When a static type checker encounters a type expression of the form ``Annotated[T, M1, M2, ...]``,
 it should enforce that for each metadata element in ``M1, M2, ...``, one of the following is true:
 
@@ -79,7 +85,7 @@ For example, to support a generic ``Gt`` metadata, one might write::
         def __init__(self, value: T) -> None:
             self.value = value
 
-        def __supports_type__(self, obj: SupportsGt[T]) -> bool:
+        def __supports_type__(self, obj: SupportsGt[T], /) -> bool:
             return obj > self.value
 
     x1: Annotated[int, Gt(0)] = 1  # OK