How can I convert pytorch model to core ml model?

Question

I trained a model and got an output named model_final.pth.

I loaded the model as below.

#load model
model = torch.load('/content/drive/MyDrive/model/model_final.pth')

And I followed the below steps.

#load sample image
input_image = Image.open("/content/drive/MyDrive/model/g0079.jpg")
display(input_image)

to_tensor = transforms.ToTensor()
input_tensor = to_tensor(input_image)
input_batch = input_tensor.unsqueeze(0)

Then when I run the code below I get an error.

#First attempt at tracing
trace = torch.jit.trace(model, input_batch)

Error:

Why am I getting this error? What do you think I should do?