Can anyone tell me what does the following code mean in the Transfer learning tutorial 218?
model_ft = models.resnet18(pretrained=True)
num_ftrs = model_ft.fc.in_features
model_ft.fc = nn.Linear(num_ftrs, 2)

I can see that this code is use to adjuest the last fully connected  layer to the ‘ant’ and ‘bee’ poblem. But I can’t find anything in the pytorch documents about .fc.in_feature, So what to do if I wants to transfer another pre-trained model, say .vgg19_bn, to another classification problem?