github上的drqv2中的main code 代码报错：*** TypeError: getattr(): attribute name must be string 。

class ExtendedTimeStep(NamedTuple):
    # step_type: Any
    # reward: Any
    # discount: Any
    # observation: Any
    # action: Any

    def __init__(self, step_type, reward, discount, observation, action):
        self.step_type = step_type
        self.reward = reward
        self.discount = discount
        self.observation = observation
        self.action = action

    def first(self):
        return self.step_type == StepType.FIRST

    def mid(self):
        return self.step_type == StepType.MID

    def last(self):
        return self.step_type == StepType.LAST

    def __getitem__(self, attr):
        return getattr(self, attr)

以上代码报错：*** TypeError: getattr(): attribute name must be string 。
经检查，发现是该class继承的NamedTuple有问题，现去掉继承的实体，并且加上__init__，如下：

# class ExtendedTimeStep(NamedTuple):
class ExtendedTimeStep:
    # step_type: Any
    # reward: Any
    # discount: Any
    # observation: Any
    # action: Any

    def __init__(self, step_type, reward, discount, observation, action):
        self.step_type = step_type
        self.reward = reward
        self.discount = discount
        self.observation = observation
        self.action = action

    def first(self):
        return self.step_type == StepType.FIRST

    def mid(self):
        return self.step_type == StepType.MID

    def last(self):
        return self.step_type == StepType.LAST

    def __getitem__(self, attr):
        return getattr(self, attr)

经验证，代码无误。