I tried code generated from vega-lite example in GraphSandbox and the rendering is broken, as the transformed code introduced a Template like content, which was treated as Mediawiki template. For people to use this more, supporting converted code from vega-lite fully would be helpful. May look at using Graph namespace and avoiding the confusion with already established template namespace usage.

Vega-lite original code url: https://vega.github.io/vega-lite/docs/transform.html

Expected rendering:

Actual rendering: