@Override
  public String toString() {
    return String.format(
        "mode=0x%s, kem_id=0x%s, kdf_id=0x%s, aead_id=0x%s",
        Hex.encode(mode), Hex.encode(kemId), Hex.encode(kdfId), Hex.encode(aeadId));
  }
Helper class for identifying different test cases.
java_src/src/main/java/com/google/crypto/tink/testing/HpkeTestId.java