Most variables are initialized as None to make sure that variables used inside the model are either explicitly initialized in the model input, or calculated inside the model. When a calculation with None is performed, Python throws a TypeError -- catching that error and displaying a better error message of why this is happening would be better than showing the "raw" Python error/traceback.
Most variables are initialized as None to make sure that variables used inside the model are either explicitly initialized in the model input, or calculated inside the model. When a calculation with None is performed, Python throws a TypeError -- catching that error and displaying a better error message of why this is happening would be better than showing the "raw" Python error/traceback.