trying to create dynamo script to count the number of seats in a room. I am following this youtube video Dynamo Basics: Count elements in Rooms - YouTube but stuck after getting this error.
I'd appreciate any help you can offer.
Creating Dynamo Script to Count Furniture(Chairs) in Room
I am not a Dynamo user or Python programmer, but it seems to me that the error message is telling you exactly what the problem is. A better place (than here in the pure Revit API discussion forum) to discuss a Dynamo- or Python-specific question like this is in the Dynamo discussion forum:
Jeremy Tammik 
Developer Advocacy and Support + The Building Coder + Autodesk Developer Network + ADN Open
Developer Advocacy and Support + The Building Coder + Autodesk Developer Network + ADN Open
