[typing] Add missing _from_iterable classmethod to Set ABCs (#15331)

Author: emmanuel-ferdman

stdlib/typing.pyi

@@ -704,6 +704,8 @@ class AbstractSet(Collection[_T_co]):
     def __contains__(self, x: object) -> bool: ...
     def _hash(self) -> int: ...
     # Mixin methods
+    @classmethod
+    def _from_iterable(cls, it: Iterable[_S]) -> AbstractSet[_S]: ...
     def __le__(self, other: AbstractSet[Any]) -> bool: ...
     def __lt__(self, other: AbstractSet[Any]) -> bool: ...
     def __gt__(self, other: AbstractSet[Any]) -> bool: ...
@@ -736,6 +738,8 @@ class MappingView(Sized):
 
 class ItemsView(MappingView, AbstractSet[tuple[_KT_co, _VT_co]], Generic[_KT_co, _VT_co]):
     def __init__(self, mapping: SupportsGetItemViewable[_KT_co, _VT_co]) -> None: ...  # undocumented
+    @classmethod
+    def _from_iterable(cls, it: Iterable[_S]) -> set[_S]: ...
     def __and__(self, other: Iterable[Any]) -> set[tuple[_KT_co, _VT_co]]: ...
     def __rand__(self, other: Iterable[_T]) -> set[_T]: ...
     def __contains__(self, item: tuple[object, object]) -> bool: ...  # type: ignore[override]
@@ -749,6 +753,8 @@ class ItemsView(MappingView, AbstractSet[tuple[_KT_co, _VT_co]], Generic[_KT_co,
 
 class KeysView(MappingView, AbstractSet[_KT_co]):
     def __init__(self, mapping: Viewable[_KT_co]) -> None: ...  # undocumented
+    @classmethod
+    def _from_iterable(cls, it: Iterable[_S]) -> set[_S]: ...
     def __and__(self, other: Iterable[Any]) -> set[_KT_co]: ...
     def __rand__(self, other: Iterable[_T]) -> set[_T]: ...
     def __contains__(self, key: object) -> bool: ...