'Most session backends don\'t need to override this method, but we do,
because instead of generating a random string, we want to actually
generate a secure url-safe Base64-encoded string of data as our
session key.'

def _get_session_key(self):

    session_cache = getattr(self, '_session_cache', {})
    return signing.dumps(session_cache, compress=True, salt='django.contrib.sessions.backends.signed_cookies', serializer=self.serializer)
