Ah! I see the issue now. You haven’t configured the Python environment.
You’re making a call to the Revit class in line 12, but the Revit class hasn’t been added to the environment yet.
See the post here for an example of why we make the various imports: Create and Export 2D Lines Loop Profile Family - #4 by jacob.small
A good boilerplate template for Revit interaction can be found here: dynamoPython/RevitPythontemplateFile at 883c11fd62c3a2b35790a5e3fed87720bcd6e557 · Amoursol/dynamoPython · GitHub