事实证明代码不是问题所在，但是我的软件出了点问题.执行以下步骤后，上面的代码将运行且没有错误或警告:

It turned out the code wasn't the problem, but there was something wrong with my software. After the following steps, the above code runs without errors or warnings:

1. 卸载anaconda
2. 安装anaconda
3. 创建新环境
4. 将所需的软件包安装到该环境中(keras，tensorflow， 间谍...)
5. 在该环境中运行代码

1. uninstall anaconda
2. install anaconda
3. create new environment
4. install required packages into that environment (keras, tensorflow, spyder...)
5. run code in that environment