Thanks for the information.
I didn’t realize that the 2 would represent the number of classes.
Usually you would use the penultimate layer from the pretrained model as the “feature” output and add a classifier on top of it. Currently pt_model.classifier[1] as well as linear3 could be seen as a classification layer and the first bottleneck might be too aggressive.
However, as always it all depends on your use case and your model might in fact work just fine.