使用tensorflow估计器头api抛出错误

我使用headapi作为 ，但抛出ValueError:可训练的_变量不能为无。如果没有，下面是代码

def _my_dnn_model_fn(features, labels, mode, params, config=None):
  # Optionally your callers can pass head to model_fn as a param.
  head = tf.estimator.MultiClassHead(3)

  feature_layer = tf.keras.layers.DenseFeatures(my_feature_columns)
  inputs = feature_layer(features)

  # Compute logits with tf.keras.layers API
  hidden_layer0 = tf.keras.layers.Dense(
      units=1000, activation="relu")(inputs)
  hidden_layer1 = tf.keras.layers.Dense(
      units=500, activation="relu")(hidden_layer0)
  logits = tf.keras.layers.Dense(
      units=head.logits_dimension, activation=None)(hidden_layer1)
  optimizer = tf.keras.optimizers.Adagrad(lr=0.1)
  return head.create_estimator_spec(
      features=features,
      labels=labels,
      mode=mode,
      logits=logits,
      optimizer=optimizer)
my_estimator = tf.estimator.Estimator(model_fn=_my_dnn_model_fn)
my_estimator.train(
    input_fn=lambda: input_fn(train, train_y, training=True),
    steps=5000)

您可以在实例化估计器段落之后运行它

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