Thank you very much! by using:

%sh apt install -y graphviz

directly on the notebook cell it does work. You've been really helpful.

Now when I run:

pymc.model_to_graphviz(model=model)

I get:

<graphviz.graphs.Digraph at 0x7f7fb2634d90>

I also tried to use the "render" method:

pm.model_to_graphviz(model=hierarchical).render()

But the output is just the string:

'.gv.pdf'

Do you know if it is possible to render the graph inside the notebook? Or otherwise where to find the graph?

Once again, thank you very much