def _get_by_sid(self, sid):
        if self._is_valid_sid(sid):
            data = memcache.get(sid)
            if data is not None:
                self.sid = sid
                return sessions.SessionDict(self, data=data)

        self.sid = self._get_new_sid()
        return sessions.SessionDict(self, new=True)
Returns a session given a session id.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/webapp2-2.3/webapp2_extras/appengine/sessions_memcache.py/MemcacheSessionFactory._get_by_sid