code: public Set<OpenPgpV4Fingerprint> getTrustedFingerprints()
              throws IOException, PGPException {
          return getFingerprintsOfKeysWithState(getAnyPublicKeys(), OpenPgpTrustStore.Trust.trusted);
      }
docs: Return a {@link Set} of {@link OpenPgpV4Fingerprint}s of all keys of the contact, which have the trust state
  {@link OpenPgpStore.Trust#trusted}.
  
  @return trusted fingerprints
  
  @throws IOException IO error
  @throws PGPException PGP error