bpo-19072: Classmethod can wrap other classmethod like descriptors (GH-29634)

staticmethod() also became callable in Python 3.10.

See: b83861f.

Author: rhettinger

Doc/howto/descriptor.rst

@@ -1264,6 +1264,9 @@ Using the non-data descriptor protocol, a pure Python version of
         def __get__(self, obj, objtype=None):
             return self.f
 
+        def __call__(self, *args, **kwds):
+            return self.f(*args, **kwds)
+
 .. testcode::
     :hide:
 
@@ -1272,13 +1275,17 @@ Using the non-data descriptor protocol, a pure Python version of
         def f(x):
             return x * 10
 
+    wrapped_ord = StaticMethod(ord)
+
 .. doctest::
     :hide:
 
     >>> E_sim.f(3)
     30
     >>> E_sim().f(3)
     30
+    >>> wrapped_ord('A')
+    65
 
 
 Class methods
@@ -1344,7 +1351,7 @@ Using the non-data descriptor protocol, a pure Python version of
             if cls is None:
                 cls = type(obj)
             if hasattr(type(self.f), '__get__'):
-                return self.f.__get__(cls)
+                return self.f.__get__(cls, cls)
             return MethodType(self.f, cls)
 
 .. testcode::