Graphviz chart comes up blank

I’m trying to use a graphviz chart for the first time. Everything else I’ve tried works. I’m using the chart definition from the user guide. The page comes up but its blank. I can create a the graphviz object in plain python and it looks correct.

My python default was 3.9, so I’ve switched back to 3.8. No change.

What can the problem be?

The issue is reported in the github repos as #1331:

st.graphviz_chart examples not rendering #1331

The fix given in there works for me in firefox and chrome, although not in edge.