Thanks so much, @ptrblck, for your prompt answer. I am not familiar with the eager model. I just guess you mean I should apply pytorch_to_keras for fine-tuning?
I work with big data, and it takes more than one week to train the model! so if I just want to change the size of a Linear layer like ( self.fc = nn.Linear(64,1)) to ( self.fc = nn.Linear(4096,1)) it is not possible, and I should modify the model and train that from the beginning?!