gh-97797: Mention __metadata__ in docstrings of typing.{_AnnotatedAlias, Annotated} (GH-103405)

miss-islington · sobolevn · AlexWaygood · web-flow · commit 0f6319fc8c01 · 2023-04-10T08:21:45.000-07:00
(cherry picked from commit dc604a8) Co-authored-by: Nikita Sobolev <mail@sobolevn.me> Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com> Co-authored-by: Kirill <80244920+Eclips4@users.noreply.github.com>
diff --git a/Lib/typing.py b/Lib/typing.py
@@ -2099,6 +2099,8 @@ class _AnnotatedAlias(_NotIterable, _GenericAlias, _root=True):
     with extra annotations. The alias behaves like a normal typing alias,
     instantiating is the same as instantiating the underlying type, binding
     it to types is also the same.
+
+    The metadata itself is stored in a '__metadata__' attribute as a tuple.
     """
     def __init__(self, origin, metadata):
         if isinstance(origin, _AnnotatedAlias):
@@ -2151,6 +2153,10 @@ class Annotated:
     Details:
 
     - It's an error to call `Annotated` with less than two arguments.
+    - Access the metadata via the ``__metadata__`` attribute::
+
+        Annotated[int, '$'].__metadata__ == ('$',)
+
     - Nested Annotated are flattened::
 
         Annotated[Annotated[T, Ann1, Ann2], Ann3] == Annotated[T, Ann1, Ann2, Ann3]
