add (overwrite with) mypy stubs, if available

stdlib/3/weakref.pyi

@@ -0,0 +1,71 @@
+# Stubs for weakref
+
+# NOTE: These are incomplete!
+
+from typing import (
+    TypeVar, Generic, Any, Callable, overload, Mapping, Iterator, Dict, Tuple,
+    Iterable, Optional
+)
+
+_T = TypeVar('_T')
+_KT = TypeVar('_KT')
+_VT = TypeVar('_VT')
+
+class ReferenceType(Generic[_T]):
+    # TODO rest of members
+    def __call__(self) -> Optional[_T]:
+        ...
+
+def ref(o: _T, callback: Callable[[ReferenceType[_T]],
+                                 Any] = None) -> ReferenceType[_T]: ...
+
+# TODO callback
+def proxy(object: _T) -> _T: ...
+
+class WeakValueDictionary(Generic[_KT, _VT]):
+    # TODO tuple iterable argument?
+    @overload
+    def __init__(self) -> None: ...
+    @overload
+    def __init__(self, map: Mapping[_KT, _VT]) -> None: ...
+
+    def __len__(self) -> int: ...
+    def __getitem__(self, k: _KT) -> _VT: ...
+    def __setitem__(self, k: _KT, v: _VT) -> None: ...
+    def __delitem__(self, v: _KT) -> None: ...
+    def __contains__(self, o: object) -> bool: ...
+    def __iter__(self) -> Iterator[_KT]: ...
+    def __str__(self) -> str: ...
+
+    def clear(self) -> None: ...
+    def copy(self) -> Dict[_KT, _VT]: ...
+
+    @overload
+    def get(self, k: _KT) -> _VT: ...
+    @overload
+    def get(self, k: _KT, default: _VT) -> _VT: ...
+
+    @overload
+    def pop(self, k: _KT) -> _VT: ...
+    @overload
+    def pop(self, k: _KT, default: _VT) -> _VT: ...
+
+    def popitem(self) -> Tuple[_KT, _VT]: ...
+
+    @overload
+    def setdefault(self, k: _KT) -> _VT: ...
+    @overload
+    def setdefault(self, k: _KT, default: _VT) -> _VT: ...
+
+    @overload
+    def update(self, m: Mapping[_KT, _VT]) -> None: ...
+    @overload
+    def update(self, m: Iterable[Tuple[_KT, _VT]]) -> None: ...
+
+    # NOTE: incompatible with Mapping
+    def keys(self) -> Iterator[_KT]: ...
+    def values(self) -> Iterator[_VT]: ...
+    def items(self) -> Iterator[Tuple[_KT, _VT]]: ...
+
+    # TODO return type
+    def valuerefs(self) -> Iterable[Any]: ...