执行第5章， train.py后提示以下几行代码，

Train on 37425 samples
Epoch 1/100
2019-08-16 18:15:15.183678: E tensorflow/core/grappler/optimizers/meta_optimizer.cc:502] constant folding failed: Invalid argument: Unsupported type: 21
2019-08-16 18:15:15.221236: E tensorflow/core/grappler/optimizers/meta_optimizer.cc:502] constant folding failed: Invalid argument: Unsupported type: 21
2019-08-16 18:15:16.736293: E tensorflow/core/grappler/optimizers/meta_optimizer.cc:502] constant folding failed: Invalid argument: Unsupported type: 21
2019-08-16 18:15:16.773799: E tensorflow/core/grappler/optimizers/meta_optimizer.cc:502] constant folding failed: Invalid argument: Unsupported type: 21

之后继续输出每次训练的loss 值

ex：
10030/37425 【=>…】 -ETA: 15:21 -loss:5.3583
.
.
一直直行到
30630/36425 【=>…】 -ETA: 15:21 -loss:4.3583Killed 结束， 也没有生成 .hdf5 文件

请问这是为什么呢？
以及该如何解决呢？