typeshed: declare that ordereddict's copy returns ordereddict

Author: Suren Nihalani

stdlib/2/collections.pyi

@@ -96,6 +96,7 @@ class Counter(Dict[_T, int], Generic[_T]):
 class OrderedDict(Dict[_KT, _VT], Reversible[_KT], Generic[_KT, _VT]):
     def popitem(self, last: bool = ...) -> Tuple[_KT, _VT]: ...
     def __reversed__(self) -> Iterator[_KT]: ...
+    def __copy__(self) -> "OrderedDict[_KT, _VT]": ...
 
 class defaultdict(Dict[_KT, _VT], Generic[_KT, _VT]):
     default_factory = ...  # type: Callable[[], _VT]

stdlib/3/collections/__init__.pyi

@@ -278,6 +278,7 @@ class OrderedDict(Dict[_KT, _VT], Reversible[_KT], Generic[_KT, _VT]):
     def popitem(self, last: bool = ...) -> Tuple[_KT, _VT]: ...
     def move_to_end(self, key: _KT, last: bool = ...) -> None: ...
     def __reversed__(self) -> Iterator[_KT]: ...
+    def __copy__(self) -> "OrderedDict[_KT, _VT]": ...
 
 class defaultdict(Dict[_KT, _VT], Generic[_KT, _VT]):
     default_factory = ...  # type: Callable[[], _VT]