No SOPClass UID after add_roi

[marrissa-mcintosh]

I am trying to create a new RT struct using a mask segmented via MATLAB and imported into Python as a numpy array. I used add_roi and then validated the RT struct using RTStructBuilder.validate_rtstruct. This throws an error "AttributeError: 'RTStruct' object has no attribute 'SOPClassUID'". The new RT struct also does not have attributes "ROIContourSequence", "StructureSetROISequence", or "RTROIObservationsSequence". Any suggestions on how to figure out what is going wrong or how to fix it would be helpful!