Fixed #26503 -- Removed an outdated example from session docs.

    >>> s['last_login']

    1376587691

In order to mitigate session fixation attacks, sessions keys that don't exist

are regenerated::

    >>> from django.contrib.sessions.backends.db import SessionStore

    >>> s = SessionStore(session_key='no-such-session-here')

    >>> s.save()

    >>> s.session_key

    'ff882814010ccbc3c870523934fee5a2'

If you're using the ``django.contrib.sessions.backends.db`` backend, each

session is just a normal Django model. The ``Session`` model is defined in

``django/contrib/sessions/models.py``. Because it's a normal model, you can