Failed to create view for 'JsmolView' from module 'jupyter-jsmol' with model 'JsmolModel' from module 'jupyter-jsmol'

[rpoteau]

Dear author this is the beginning of a message obtained in a jupyer notebook, after calling this piece of code

JSMol = JsmolView(
    layout=Layout(height="300px", width="300px"), 
    info={'color':'#e2e2e2'}
)

display(JSMol)

JSMol.load_file("./Molecules-data/anisole.mol",inline=True)

The full message is

ReferenceError: Jmol is not defined
    at i.render (http://localhost:8888/lab/extensions/jupyter-jsmol/static/261.41f850f7554071854068.js?v=41f850f7554071854068:1:1233)
    at http://localhost:8888/static/lab/4416.74698273b3de2ad84746.js?v=74698273b3de2ad84746:1:4434
    at async w.renderModel (http://localhost:8888/lab/extensions/@jupyter-widgets/jupyterlab-manager/static/446.fdf8b1b233cb8c1783f6.js?v=fdf8b1b233cb8c1783f6:1:72328)

Is it related to the fact that installing extensions with the jupyter labextension install command is now deprecated?

Any help will be most welcome Regards Romuald