Function yours_at 

fn yours_at(root: &Path, fingerprint: &str) -> bool

Whether the certificate fingerprint (hexadecimal) is one of yours in the folder root (pgp/): kept with your keys, a security key’s read here, or one your other devices made known (cards/), as a phone knows your security key’s certificate: never kept among others’ keys, from wherever it comes again (your own mail’s Autocrypt header, a lookup).