Errors in `Calculator.asset_bubble()` method

[jdebacker]

After creating two Calculator objects, named calc1 and calc2 and running:

bplot = calc1.asset_bubble(calc2)
show(bplot)

two warning messages result:

WARNING:bokeh.core.validation.check:W-1000 (MISSING_RENDERERS): Plot has no renderers: Figure(id='1663', ...)
WARNING:bokeh.core.validation.check:W-1000 (MISSING_RENDERERS): Plot has no renderers: Figure(id='1720', ...)

And no Bokeh plot object is displayed. This error the results in no plot object being created seems to have arisen with more recent versions of Bokeh, although the widget has never come out looking exactly as one would like it.

An example of instantiating and running these Calculator objects and calling the asset_bubble method of the Calculator class is provided in PSL_demo.ipynb (in the documentation here.

The result looks like the following:

Execution results in two warnings and the resulting plot is missing the key showing the mapping between total assets and bubble size (which used to appear in a box under "Asset Size" at the bottom of the figure).