Issue #28003: Implement PEP 525 -- Asynchronous Generators.
diff --git a/Lib/types.py b/Lib/types.py
index 48891cd..d8d8470 100644
--- a/Lib/types.py
+++ b/Lib/types.py
@@ -24,6 +24,11 @@
 CoroutineType = type(_c)
 _c.close()  # Prevent ResourceWarning
 
+async def _ag():
+    yield
+_ag = _ag()
+AsyncGeneratorType = type(_ag)
+
 class _C:
     def _m(self): pass
 MethodType = type(_C()._m)