当我将列表对象添加到keras子类模型时，`tf.model_to_estimator`引发AttributeError

import tensorflow as tf
from tensorflow.keras import layers

class MyModel(tf.keras.Model):
    def __init__(self):
        super(MyModel, self).__init__()
        self.dense = layers.Dense(64, activation='relu')
        self.out = layers.Dense(10, activation='softmax')
        
    def call(self, inputs):
        x = self.dense(inputs)
        return self.out(x)

# 创建一个Keras子类模型的实例
model = MyModel()

# 转换为Keras函数式模型
inputs = tf.keras.Input(shape=(input_shape,))
outputs = model.call(inputs)
functional_model = tf.keras.Model(inputs=inputs, outputs=outputs)

# 使用tf.model_to_estimator将函数式模型转换为估计器
estimator = tf.keras.estimator.model_to_estimator(keras_model=functional_model)

import tensorflow as tf
from tensorflow.keras import layers

# 创建一个Keras函数式模型
inputs = tf.keras.Input(shape=(input_shape,))
x = layers.Dense(64, activation='relu')(inputs)
outputs = layers.Dense(10, activation='softmax')(x)
functional_model = tf.keras.Model(inputs=inputs, outputs=outputs)

# 使用tf.model_to_estimator将函数式模型转换为估计器
estimator = tf.keras.estimator.model_to_estimator(keras_model=functional_model)