'Check if there are any users who have stopped syncing a while ago
and haven\'t come back yet. If there are poke the master about them.'

def send_stop_syncing(self):

    now = self.clock.time_msec()
    for (user_id, last_sync_ms) in self.users_going_offline.items():
        if ((now - last_sync_ms) > (10 * 1000)):
            self.users_going_offline.pop(user_id, None)
            self.send_user_sync(user_id, False, last_sync_ms)
