"Pre-built extensions" without bokeh server

Hello,
I have been happily using the very nice inline Bokeh extension mechanism, but I have gotten to the point where I want to have two classes derived from ColumnDataSource share a common third class derived from DataSource. So I’ve embarked on the path set out in pre-built extensions. I haven’t gotten there yet, but I am beginning to wonder if prebuilt extensions are only useful if the Bokeh server is used? If they can be used with just web-browser plotting, what hook is used to load the pre-built extension so that it can be referenced from the Python classes? In other words, once I have the extension, how do I use it?

Does anyone know if this is the case? In my case, the Bokeh Python functions are called from the user’s python session, so no Bokeh server is available.

Thanks very much for any advice!

cc @Philipp_Rudiger @mateusz can one of you comment?