docs: public OmemoFingerprint getFingerprint(OmemoDevice userDevice, OmemoDevice contactsDevice)
              throws CorruptedOmemoKeyException, NoIdentityKeyException {
  
          T_IdKey identityKey = loadOmemoIdentityKey(userDevice, contactsDevice);
          if (identityKey == null) {
              throw new NoIdentityKeyException(contactsDevice);
          }
          return keyUtil().getFingerprintOfIdentityKey(identityKey);
      }