code: public void trust(OpenPgpV4Fingerprint fingerprint)
              throws IOException {
          store.setTrust(getJid(), fingerprint, OpenPgpTrustStore.Trust.trusted);
      }
docs: Mark a key as {@link OpenPgpStore.Trust#trusted}.
  
  @param fingerprint {@link OpenPgpV4Fingerprint} of the key to mark as trusted.
  
  @throws IOException IO error