How does one bypass the iCloud lock on a MacBook?

I bought a MacBook Air from someone, and they didn't properly factory reset it. I am currently trying to reset it, but when going to Recovery mode via the Internet to proceed further, it requires the person's Apple ID. So far I've tried to get in contact with the person, but they no longer respond. Is there any course of action other than selling it for parts as it’s still in perfect working order?