Description
iris_dnn 训练模型后并未输出 'accuracy'、'average_loss'、'loss'、'global_step' 等信息.

Reproduction Steps

1. 打开 sql-machine-learning, 点击进入 Quick Start
2. 点击进入 SQLFlowPlayground On the Cloud
3. 点击进入 iris-dnn.ipynb
4. 执行训练语句:

%%sqlflow SELECT * FROM iris.train TO TRAIN DNNClassifier WITH model.n_classes = 3, model.hidden_units = [10, 10], train.epoch = 10 COLUMN sepal_length, sepal_width, petal_length, petal_width LABEL class INTO `sqlflow_models.my_dnn_model; 

5. 查看训练语句中输出信息, 发现与下面 markdown 注释中不同 (缺少准确率等信息)

Expected Behavior
希望训练模型后, 可以输出 'accuracy'、'average_loss'、'loss'、'global_step' 等信息, 方便调优时查看结果.

Screenshots

同样的问题出现在使用sqlflow命令行操作自定义mysql数据源中

Environment (Please complete the following information):

• OS: linux
• Browser: chrome
• Version:

Additional Notes