This is because "code" is a standard python module

https://docs.python.org/3/library/code.html

to fix this issue, I think the Intersystems developpers should hide user-made code in a custom module so it doesn't conflict when trying to load it

Very nice extension,

I have myself experimented with PlantUML diagrams generation and made my own bare-bone python script in the past, but you have nailed it as a fully automated vscode extension with integrated preview. Good work.