无法将多个回调传递给keras模型

from keras.callbacks import Callback

class CustomCallback(Callback):
    def __init__(self, callbacks):
        super(CustomCallback, self).__init__()
        self.callbacks = callbacks

    def on_train_begin(self, logs=None):
        for callback in self.callbacks:
            callback.on_train_begin(logs)

    def on_epoch_end(self, epoch, logs=None):
        for callback in self.callbacks:
            callback.on_epoch_end(epoch, logs)

    # 其他需要重写的回调函数方法...

# 创建多个回调函数实例
callback1 = Callback1()
callback2 = Callback2()
callback3 = Callback3()

# 创建自定义回调函数，并将多个回调函数传递给它
custom_callback = CustomCallback(callbacks=[callback1, callback2, callback3])

# 将自定义回调函数传递给模型的fit()方法
model.fit(x_train, y_train, callbacks=[custom_callback])