Do PNU (Positive-Negative-Unlabelled) methods expand to non-binary classification

Looking at various materials for PNU Semi-Supervised Learning, they seem to be all based around binary classification, as the name implies. How easy is to apply these methods to classifications with multiple labels? So, rather than just Is this a cat?, we have Is this a cat?, Is this a dog?, Is this a horse?, etc. Or in this situation are other approaches better?

I saw this question, but it didn't really help my understanding.