<!-- Put in HTML file-->
<!--
JS
parent_dir is reletive to Flask app.py dir
meaning: /main/app.py
/main/parent_dir/file.js
-->
<script src="{{url_for('parent_dir', filename='file.js')}}"></script>
<!--
CSS
parent_dir is reletive to Flask app.py dir
meaning: /main/app.py
/main/parent_dir/file.css
-->
<link href="{{ url_for("parent_dir",filename="file.css") }}" rel="stylesheet">