Tenant keeping unauthorized pet

[Sadia Abbasi]

I have a tenant in one of the units of a duplex in which I live. I am in the process of selling the duplex (Pittsburgh, PA). I had a realtor coming in to take pictures of the house and saw that my tenant had a snake in one of the rooms (of course hidden). On the pet addendum, this tenant mentioned that she had a cat and a dog.  It does say on the lease that no other pet should be brought in on the property other than the ones mentioned. Now I don't know for how long she had that snake for. I didn't see it either given I don't go to her property. She clearly broke the lease. Please recommend the actions steps that I can/should take.