diff --git a/extensions/mypy_extensions.py b/extensions/mypy_extensions.py
index efa3c35e8e03..26e568cc0a27 100644
--- a/extensions/mypy_extensions.py
+++ b/extensions/mypy_extensions.py
@@ -22,9 +22,11 @@ def _check_fails(cls, other):
         pass
     return False
 
+
 def _dict_new(cls, *args, **kwargs):
     return dict(*args, **kwargs)
 
+
 def _typeddict_new(cls, _typename, _fields=None, **kwargs):
     if _fields is None:
         _fields = kwargs
@@ -33,6 +35,7 @@ def _typeddict_new(cls, _typename, _fields=None, **kwargs):
                         " but not both")
     return _TypedDictMeta(_typename, (), {'__annotations__': dict(_fields)})
 
+
 class _TypedDictMeta(type):
     def __new__(cls, name, bases, ns):
         # Create new typed dict class object.
@@ -88,3 +91,7 @@ class Point2D(TypedDict):
     The latter syntax is only supported in Python 3.6+, while two other
     syntax forms work for Python 2.7 and 3.2+
     """
+
+
+# Return type that indicates a function does not return
+class NoReturn: pass