Saving a fine-tuned model

How do I save a model, using Huggingface, after adding tensorflow layers to it. I am able to save it using native tensorflow, but not Huggingface. Specifially, I am using “model = TFBertModel.from_pretrained(‘bert-base-cased’)”, and then adding a few layers to it. After I add the layers it is no longer saveable using transformers. I get the error “AttributeError: ‘Functional’ object has no attribute ‘save_model’”. Please help.