Traceback (most recent call last):
File "./stepcvt_export_all.py", line 74, in <module>
for partid, obj in source.parts():
File "stepcvt/stepcvt/project.py", line 62, in parts
assemblies = self._CADSource__step.assemblies
AttributeError: 'NoneType' object has no attribute 'assemblies'
fails with this error: