I have been following the ants and bees transfer learning tutorial from the official PyTorch Docs (http://pytorch.org/tutorials/beginner/transfer_learning_tutorial.html). I am trying to finetune a VGG19 model by changing the final layer to predict one of two classes. I am able to modify the last fc layer using the following code.

But I get an error when executing the train_model function. The error is “size mismatch at /opt/conda/conda-bld/pytorch_1513368888240/work/torch/lib/THC/generic/THCTensorMathBlas.cu:243”. Any idea what the issue is ?

```
model_conv = torchvision.models.vgg19(pretrained=True)
for param in model_conv.parameters():
param.requires_grad = False
model_conv = nn.Sequential(*list(model_conv.classifier.children())[:-1] +
[nn.Linear(in_features=4096, out_features=2)])
if use_gpu:
model_conv = model_conv.cuda()
criterion = nn.CrossEntropyLoss()
optimizer_conv = optim.SGD(model_conv._modules['6'].parameters(), lr=0.001, momentum=0.9)
exp_lr_scheduler = lr_scheduler.StepLR(optimizer_conv, step_size=7, gamma=0.1)
model_conv = train_model(model_conv, criterion, optimizer_conv, exp_lr_scheduler, num_epochs=25)
```