code: public OpenPgpV4Fingerprint getSigningKeyFingerprint() throws IOException, PGPException {
          PGPSecretKeyRing signingKeyRing = getSigningKeyRing();
          return signingKeyRing != null ? new OpenPgpV4Fingerprint(signingKeyRing.getPublicKey()) : null;
      }
docs: Return the {@link OpenPgpV4Fingerprint} of our signing key.
  @return fingerprint of signing key
  @throws IOException IO is dangerous
  @throws PGPException PGP is brittle