Hello Baosen,

To make a prediction on a new class, you can load the pre-trained weights for the Mask R-CNN, exclude the last few layers, and train the model.

The concept of Transfer learning is applied where we freeze all the weights of the base pre-trained model and add a few layers on the top of the pre-trained model to identify the new class or new set of classes.

I hope the answer helps

Thanks,

Renu