How to do online-training: Feed data loop by loop

How can I specify the specific files to use each epoch in the multiclass lesson 2? Can I change the csv or json file?

I’m looking at https://github.com/fastai/fastai/blob/master/courses/dl1/lesson2-image_models.ipynb

Can I just keep calling learn = ConvLearner.pretrained(f_model, data, metrics=metrics) ? It seems like it relearns each time.