def save(self):
'''Saves the session data to the datastore.'''
time_till_expire = timedelta(seconds=settings.SESSION_COOKIE_AGE)
expire_date = datetime.now() + time_till_expire
if self._datastore_session:
self._datastore_session.session_data = self.encode(self._session)
else:
self._datastore_session = Session(session_key=self.session_key,
session_data=self.encode(
self._session),
expire_date=expire_date)
self._datastore_session.put()
