def tick(self):
        if self.callback:
            return self.callback()
Decodes a value using urllib.unquote and deserializes it from JSON.
dataset/ETHPy150Open RobotLocomotion/director/src/python/director/timercallback.py/TimerCallback.tick--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/webapp2-2.5.1/webapp2_extras/json.py/unquote