image(s) that are not contained in input series

[karllandheer]

Hello, thank you very much for the great package. When running it, I got this error when loading an RT struct:

At line 400: <class 'Exception'>: Loaded RTStruct references image(s) that are not contained in input series data. Problematic image has SOP Instance Id: 1.2.752.37.5.626934496.20190830.24838.6.2067

I understand this is from a check, but what exactly is being checked?