add stubs for frozendict (#4522)

third_party/3/frozendict.pyi

@@ -0,0 +1,27 @@
+import collections
+from typing import Any, Dict, Generic, Iterable, Iterator, Mapping, Tuple, Type, TypeVar, overload
+
+_S = TypeVar("_S")
+_KT = TypeVar("_KT")
+_VT = TypeVar("_VT")
+
+class frozendict(Mapping[_KT, _VT], Generic[_KT, _VT]):
+
+    dict_cls: Type[Dict] = ...
+    @overload
+    def __init__(self, **kwargs: _VT) -> None: ...
+    @overload
+    def __init__(self, mapping: Mapping[_KT, _VT]) -> None: ...
+    @overload
+    def __init__(self, iterable: Iterable[Tuple[_KT, _VT]]) -> None: ...
+    def __getitem__(self, key: _KT) -> _VT: ...
+    def __contains__(self, key: object) -> bool: ...
+    def copy(self: _S, **add_or_replace: _VT) -> _S: ...
+    def __iter__(self) -> Iterator[_KT]: ...
+    def __len__(self) -> int: ...
+    def __repr__(self) -> str: ...
+    def __hash__(self) -> int: ...
+
+class FrozenOrderedDict(frozendict):
+
+    dict_cls: Type[collections.OrderedDict] = ...