Add stub for queue.SimpleQueue in 3.7 (#2995)

Closes: #2994

stdlib/3/queue.pyi

@@ -4,6 +4,7 @@
 
 from collections import deque
 from typing import Any, TypeVar, Generic, Optional
+import sys
 
 _T = TypeVar('_T')
 
@@ -30,3 +31,13 @@ class Queue(Generic[_T]):
 
 class PriorityQueue(Queue[_T]): ...
 class LifoQueue(Queue[_T]): ...
+
+if sys.version_info >= (3, 7):
+    class SimpleQueue(Generic[_T]):
+        def __init__(self) -> None: ...
+        def empty(self) -> bool: ...
+        def get(self, block: bool = ..., timeout: Optional[float] = ...) -> _T: ...
+        def get_nowait(self) -> _T: ...
+        def put(self, item: _T, block: bool = ..., timeout: Optional[float] = ...) -> None: ...
+        def put_nowait(self, item: _T) -> None: ...
+        def qsize(self) -> int: ...