Exmaple fixes

Author: warsaw

peps/pep-0813.rst

@@ -83,7 +83,7 @@ A new argument to built-in ``print``
 Built-in :func:`print` takes a new optional argument, appended to the end of the argument list, called
 ``pretty``, which can take one of the following values:
 
-* ``None`` - the default; fully backward compatible
+* ``None`` - the default. No pretty printing is invoked.  Fully backward compatible
 * ``True`` - use a temporary instance of the :py:class:`python:pprint.PrettyPrinter` class to get a
   pretty representation of the object.
 * An instance with a ``pformat()`` method, which has the same signature as
@@ -103,7 +103,8 @@ A custom ``__pprint__()`` method can be used to customize the representation of
     >>> class Custom:
     ...     def __str__(self): return 'my str'
     ...     def __repr__(self): return 'my repr'
-    ...     def __pprint__(self, context, maxlevels, level): return 'my pprint'
+    ...     def __pprint__(self, context, maxlevels, level):
+    ...         return 'my pprint', False, False
 
     >>> pprint.pp(Custom())
     my pprint