Re-train the fine tune model for new class

Hi, I have fine-tune the classification model for 38 classes. Now I want to re-train the fine-tune only with only 1 new class.

So I have loaded checkpoint from last fine-tune model like that
How I can do that, please find my code below

retrain_model = SentenceTagger.load_from_checkpoint(
    n_training_steps= total_training_steps

But getting error like,
RuntimeError: Error(s) in loading state_dict for SentenceTagger:
size mismatch for classifier.weight: copying a param with shape torch.Size([38, 768]) from checkpoint, the shape in current model is torch.Size([1, 768]).
size mismatch for classifier.bias: copying a param with shape torch.Size([38]) from checkpoint, the shape in current model is torch.Size([1]).

I have look different forum to solve the issue. I have tried skip_mismatch=True but doesn’t help