Does pyvista/trame require ipywidgets? Also, should we use trame-jupyter-extension by default?

[johnkit]

When I install from the pyvista-xarray source and run the examples, Jupyter displays a static image and a warning that it "Failed to use notebook backend" and instructs me to install ipywidgets. Screenshot is below.

• Installing ipywidgets fixes the problem. Is there something in our code that requires ipython?
• Separate from that: should we include trame-jupyter-extension in the examples/requirements.txt?, My understanding is that the extension is only needed when using a remote Jupyter server on a host with port constraints, but perhaps we should standardize on including the extension by default?
• Oh, and because I just noticed, I think we also need to update the examples/requirements.txt file to change pyvista to pyvista[trame].

[jourdain]

I guess it you aim to use it in jupyter, you should install pyvista[jupyter]