在实验平台Buckland_Chapter3-Steering Behaviors中带优先级的抖动的代码是？

以下是带优先级的抖动代码：

class WanderAndAvoid(object):
    def __init__(self, agent, world, priority):
        self.agent = agent
        self.world = world
        self.priority = priority
        self.wander_force = Wander(agent)
        self.avoid_force = Avoid(agent, world)

    def getSteering(self):
        wander_steering = self.wander_force.getSteering()
        avoid_steering = self.avoid_force.getSteering()

        if avoid_steering != None:
            return avoid_steering

        if wander_steering != None:
            return wander_steering

        return None
``