public static final KeyTemplate rawAes256GcmSivTemplate() {
    return exceptionIsBug(
        () ->
            KeyTemplate.createFrom(
                AesGcmSivParameters.builder()
                    .setKeySizeBytes(32)
                    .setVariant(AesGcmSivParameters.Variant.NO_PREFIX)
                    .build()));
  }
Creates and returns a {@link KeyTemplate} that generates new instances of AES-GCM-SIV with the
following parameters:

<ul>
  <li>Key size: 32 bytes
  <li>Prefix type: {@link KeyTemplate.OutputPrefixType#RAW} (no prefix)
</ul>

<p>Keys generated from this template should create ciphertexts compatible with other libraries.
java_src/src/main/java/com/google/crypto/tink/aead/AesGcmSivKeyManager.java