Issue #10771: Clarify that descriptors get used in an *owner* class or one of its parents.

Doc/reference/datamodel.rst

@@ -1539,11 +1539,11 @@ Implementing Descriptors
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
 The following methods only apply when an instance of the class containing the
-method (a so-called *descriptor* class) appears in the class dictionary of
-another new-style class (known as the *owner* class) or one of its
-descendants.  In the examples below, "the attribute" refers to the attribute
-whose name is the key of the property in the owner class' ``__dict__``.
-Descriptors can only be implemented as new-style classes themselves.
+method (a so-called *descriptor* class) appears in an *owner* class (the
+descriptor must be in either the owner's class dictionary or in the class
+dictionary for one of its parents).  In the examples below, "the attribute"
+refers to the attribute whose name is the key of the property in the owner
+class' :attr:`__dict__`.
 
 
 .. method:: object.__get__(self, instance, owner)