Use of external javascript library break notebook?

I want to use a simple javascript library for flow chart with panel.

How to do this ?
Here is what I try based on

First cells are:

css = ['']
js = {
    '$': '',
    'JQUI': '',
    'FlowChart': ''

pn.extension(css_files=css, js_files=js)

I cannot add any other cells after.

Can somebody help me ?