Make context manager example likelier

pep-0008.txt

@@ -837,14 +837,15 @@ Programming Recommendations
           # Will also catch KeyError raised by handle_value()
           return key_not_found(key)
 
-- Context managers should be in separate classes whenever they do
-  something other than acquire and release resources.  For example:
+- Context managers should be invoked through separate functions or methods
+  whenever they do something other than acquire and release resources.
+  For example:
 
-      Yes:     with auto_commit_or_rollback(conn):
-                   do_transaction(conn)
+      Yes:     with conn.begin_transaction():
+                   do_stuff_in_transaction(conn)
 
       No:      with conn:
-                   do_transaction(conn)
+                   do_stuff_in_transaction(conn)
 
    The latter example doesn't provide any information to indicate that
    the __enter__ and __exit__ methods are doing something other than