docs: public OmemoFingerprint getFingerprint(OmemoDevice userDevice)
              throws CorruptedOmemoKeyException {
  
          T_IdKeyPair keyPair = loadOmemoIdentityKeyPair(userDevice);
          if (keyPair == null) {
              return null;
          }
  
          return keyUtil().getFingerprintOfIdentityKey(keyUtil().identityKeyFromPair(keyPair));
      }