Try this:

"Source code: ROMondrianExample>>treeLayoutOn:"
"Preambule. It includes the initialization. "
| view rawView |
rawView := ROView new.
view := ROMondrianViewBuilder view: rawView.
"-------------"
"-------------"

    view shape rectangle size: 20.
    view nodes: ( Magnitude withAllSubclasses flatCollect: [ :e | e methodDict values ]) .
    view edgesFrom: [ :e | [e superclass] on: Exception do: [ e methodClass ]  ].
    view layout: ROTreeLayout  .
    
    "view edges do: [ :e | e - ROLine ]."

"-------------"
"-------------"
"Below is the initiation of the menu and opening the visualization"
ROEaselMorphic new populateMenuOn: view.
view open

Regards

Mathieu