I have a network consist of two parts.I want to train the first part alone to get a pth file.then,modify the code to add the second part into my network,the first part is not modified.now load and freeze the first pre-trained part,train the second one,and finally generate a whole pth file.I’m confused about how to write the code in my training loop.I use pretrained vgg inside my network, but I write down the load and freeze code inside the architecture,not the train loop.What if I want to load my own pth file and freeze some part of my network in the training code?