Annotate known magic-method return types (#9131)

stubs/babel/babel/localedata.pyi

@@ -16,7 +16,7 @@ class Alias:
 class LocaleDataDict(MutableMapping[Any, Any]):
     base: Any
     def __init__(self, data, base: Any | None = ...) -> None: ...
-    def __len__(self): ...
+    def __len__(self) -> int: ...
     def __iter__(self): ...
     def __getitem__(self, key): ...
     def __setitem__(self, key, value) -> None: ...

stubs/babel/babel/messages/catalog.pyi

@@ -81,7 +81,7 @@ class Catalog:
     @property
     def plural_forms(self): ...
     def __contains__(self, id): ...
-    def __len__(self): ...
+    def __len__(self) -> int: ...
     def __iter__(self): ...
     def __delitem__(self, id) -> None: ...
     def __getitem__(self, id): ...

stubs/babel/babel/support.pyi

@@ -23,7 +23,7 @@ class LazyProxy:
     def __bool__(self) -> bool: ...
     def __dir__(self): ...
     def __iter__(self): ...
-    def __len__(self): ...
+    def __len__(self) -> int: ...
     def __add__(self, other): ...
     def __radd__(self, other): ...
     def __mod__(self, other): ...