Sqlalchemy's session usage in web. py

According to the sqlalchemy document, the lifecycle of the sqlalchemy session in the web application context should be:

Web Server          Web Framework        User-defined Controller Call
--------------      --------------       ------------------------------
web request    ->
                    call controller ->   # call Session().  this establishes a new,
                                         # contextual Session.
                                         session = Session()

                                         # load some objects, save some changes
                                         objects = session.query(MyClass).all()

                                         # some other code calls Session, it's the
                                         # same contextual session as "sess"
                                         session2 = Session()
                                         session2.add(foo)
                                         session2.commit()

                                         # generate content to be returned
return generate_content()
                    Session.remove() <-
web response   <-

See: http://www.sqlalchemy.org/docs/05/session.html#lifespan-of-a-contextual-session

However, in the example of using sqlalchemy In the cookbook of web. py, the session resource of sqlalchemy is not released at the end, which should be as follows:

Def load_sqla (handler ):
Web. ctx. orm = scoped_session (sessionmaker (bind = engine ))
Try:
Return handler ()
Failed T web. HTTPError:
Web. ctx. orm. commit ()
Raise
Except t:
Web. ctx. orm. rollback ()
Raise
Finally:
Web. ctx. orm. commit ()
# If the above alone doesn' t work, uncomment
# The following line:
# Web. ctx. orm. expunge_all ()
Web. ctx. orm. close () # <=-close the session, or use. remove ()