Please provide example for using graphviz

I've set both the htmlGraphviz and htmlSyntaxHighlighting preferences to Yes, but I still cannot get any graphviz syntax rendered. I guess I need to do more than just write graphviz notation into an .md document, but what is it? There seems to be no documentation for how to do this.

At least add a page to the wiki with an example, please.

Start by checking how the htmlGraphviz and htmlSyntaxHighlighting preferences are implemented and reviewing the existing wiki or documentation entry points. Confirm the required Graphviz notation and rendering setup, then add a working example that explains the steps and produces rendered output.

Written by the indexing model from the issue text.