Jupyter notebook Markdown cell not get rendered properly in github

Refer to this issue: https://stackoverflow.com/questions/52694806/jupyter-notebook-on-github-bash-command-shown-as-validation-error

Somehow the background color of the code block is overridden to '#fff',

```
.rendered_html pre, .rendered_html (from: https://render.githubusercontent.com/assets/ipynb-cdc8a2c29b9e77afb5ead41e895d2850.css)

code {
border: 0;
background-color: #fff;
color: #000;
font-size: 100%;
padding: 0;
}
```

It works fine in Jupyter notebook page, but not in github page.

Start with the linked Stack Overflow report and inspect the cited ipynb-cdc8a2c29b9e77afb5ead41e895d2850.css rules for rendered Markdown code blocks. Confirm where the GitHub rendering stylesheet is controlled and reproduce the Bash command case; done means the code block no longer receives the incorrect white background or validation-error appearance on GitHub.

Written by the indexing model from the issue text.