@Override
  public MessageLite newKey(ByteString serializedKeyFormat) throws GeneralSecurityException {
    try {
      HmacKeyFormat format =
          HmacKeyFormat.parseFrom(serializedKeyFormat, ExtensionRegistryLite.getEmptyRegistry());
      return newKey(format);
    } catch (InvalidProtocolBufferException e) {
      throw new GeneralSecurityException("expected serialized HmacKeyFormat proto", e);
    }
  }
@param serializedKeyFormat serialized {@code HmacKeyFormat} proto
@return new {@code HmacKey} proto
java_src/src/main/java/com/google/crypto/tink/mac/internal/LegacyHmacTestKeyManager.java