code: 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);
      }
docs: Return the fingerprint of the identityKey belonging to contactsDevice.
  
  @param userDevice our OmemoDevice.
  @param contactsDevice OmemoDevice we want to have the fingerprint for.
  @return fingerprint of the userDevices IdentityKey.
  @throws CorruptedOmemoKeyException if the IdentityKey is corrupted.
  @throws NoIdentityKeyException if no IdentityKey for contactsDevice has been found locally.