remove nested from __all__
diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index d14c07b..e26d77a 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -4,7 +4,7 @@
 from functools import wraps
 from warnings import warn
 
-__all__ = ["contextmanager", "nested", "closing"]
+__all__ = ["contextmanager", "closing"]
 
 class GeneratorContextManager(object):
     """Helper for @contextmanager decorator."""