#16832: s/integer/object/ in docs/docstring, and add whatsnew entry.

Doc/library/abc.rst

@@ -318,9 +318,9 @@ The :mod:`abc` module also provides the following functions:
 
    Returns the current abstract base class cache token.
 
-   The token is an opaque integer identifying the current version of the
-   abstract base class cache for virtual subclasses. This number changes
-   with every call to :meth:`ABCMeta.register` on any ABC.
+   The token is an opaque object (that supports equality testing) identifying
+   the current version of the abstract base class cache for virtual subclasses.
+   The token changes with every call to :meth:`ABCMeta.register` on any ABC.
 
    .. versionadded:: 3.4
 

Doc/whatsnew/3.4.rst

@@ -473,6 +473,12 @@ trace memory blocks allocated by Python. It provides the following information:
 Improved Modules
 ================
 
+abc
+---
+
+New function :func:`abc.get_cache_token` can be used to know when to invalidate
+caches that are affected by changes in the object graph.  (Contributed
+by Łukasz Langa in :issue:`16832`.)
 
 aifc
 ----

Lib/abc.py

@@ -241,8 +241,8 @@ class ABC(metaclass=ABCMeta):
 def get_cache_token():
     """Returns the current ABC cache token.
 
-    The token is an opaque integer identifying the current version of
-    the ABC cache for virtual subclasses. This number changes with
-    every call to ``register()`` on any ABC.
+    The token is an opaque object (supporting equality testing) identifying the
+    current version of the ABC cache for virtual subclasses. The token changes
+    with every call to ``register()`` on any ABC.
     """
     return ABCMeta._abc_invalidation_counter