v.to_html() shows empty space (without the globe)

[Huyston]

I'm testing cesiumpy both in Jupyter notebook and in html mode. It works as expected in Jupyter notebook after installing ipywidgets (pip install ipywidgets).

In html, however, the viewer loads but there is only empty space (without the globe). What can I do to fix it.
I wrote a file index.html with the v.to_html() method.

Thanks

[astrojuanlu]

Possibly related: #77

[WillardFarmer]

This issue isn't related to #77. Rather you need to specify an imagery provider such as ArcGIS.