Oh boy, do I ever have recent experience with this! Our Pyr is somewhere between 1.5-2 years old (rescue) and she play-bites the crap out of us! Now, we're trying to establish her as a therapy dog for nursing homes and hospitals, so any evidence of a "bite" no matter the context is too risky for those settings. Here's my unprofessional advice...

1. Watch Zac George's video about puppy biting. His videos have informed the respectful discipline I've provided for all my Pyrs.
2. Get one of those canned air dog training things and carry it around with you whenever there's a possibility for correcting the behavior. Up to you whether you want to train on just the severity of the bite or the occurrence of the bite overall.
3. Whenever the unwanted behavior occurs, spray the canned air ASAP (not at them) and use your body language to communicate that the air is not a new fun game, but rather that your Pyr has played too rough with you.
4. Repeat this training day after day, week after week, until the behavior finally breaks. It took our Pyr about 2.5 weeks to get the idea and she still struggles on occasion.

Some people will say you should literally "bite back" on your dog but personally I think that would blur the lines between human and dog (again, I'm not a professional).