add (overwrite with) mypy stubs, if available

stdlib/3/heapq.pyi

@@ -0,0 +1,18 @@
+# Stubs for heapq
+
+# Based on http://docs.python.org/3.2/library/heapq.html
+
+from typing import TypeVar, List, Iterable, Any, Callable
+
+_T = TypeVar('_T')
+
+def heappush(heap: List[_T], item: _T) -> None: ...
+def heappop(heap: List[_T]) -> _T: ...
+def heappushpop(heap: List[_T], item: _T) -> _T: ...
+def heapify(x: List[_T]) -> None: ...
+def heapreplace(heap: List[_T], item: _T) -> _T: ...
+def merge(*iterables: Iterable[_T]) -> Iterable[_T]: ...
+def nlargest(n: int, iterable: Iterable[_T],
+             key: Callable[[_T], Any] = None) -> List[_T]: ...
+def nsmallest(n: int, iterable: Iterable[_T],
+              key: Callable[[_T], Any] = None) -> List[_T]: ...