How to inherit only parts of weights?

For example, at the beginning there are 10 classes images, and each image’s feature vector is 100 dimension vector, so the classifier weight matrix is 100*10.

Then I get 5 new classes images, so the weight matrix would be 100*15.

So the question is how can I inherit and fix the previous 100*10 matrix, which means that we just only fine-tune the 100*5 matrix.

Can this be implemented easily? Thanks so much!