issue with "boreal.spectrum('beatles.wav')"

[mathieulagrange]

when running the demonstration notebook using vscode, the import is fine but the command "boreal.spectrum('beatles.wav')" returns:

---

ValueError Traceback (most recent call last)
/var/folders/zw/1s3px2yx3s376fj348dlvj5h0000gp/T/ipykernel_71994/141500260.py in
1 # show a reactive audio spectrum widget
----> 2 boreal.spectrum('beatles.wav')

~/tools/boreal/boreal/boreal.py in spectrum(audio_input, playback_mode, notebook_url)
78 """ Spectrum audio widget
79 """
---> 80 render(audio_input, ['spectrum'], playback_mode, notebook_url)
81
82

~/tools/boreal/boreal/boreal.py in render(audio_input, widgets, playback_mode, notebook_url)
70 print(notebook_url)
71 output_notebook(resources=INLINE)
---> 72 show(app, notebook_url=notebook_url)
73
74

~/opt/anaconda3/lib/python3.9/site-packages/bokeh/io/showing.py in show(obj, browser, new, notebook_handle, notebook_url, **kwargs)
151 # in Tornado) just in order to show a non-server object
152 assert state.notebook_type is not None
--> 153 return run_notebook_hook(state.notebook_type, 'app', obj, state, notebook_url, **kwargs)
154
...
--> 157 raise ValueError("Empty host value")
158 hosts.append(host+":80")
159 elif len(parts) == 2:

ValueError: Empty host value