@RestrictedApi(
      explanation = "Accessing parts of keys can produce unexpected incompatibilities, annotate the function with @AccessesPartialKey",
      link = "https://developers.google.com/tink/design/access_control#accessing_partial_keys",
      allowedOnPath = ".*Test\\.java",
      allowlistAnnotations = {AccessesPartialKey.class})
  public SecretBytes getKeyBytes() {
    return keyBytes;
  }
Represents the Aead ChaCha20-Poly1305 specified in RFC 8439.

<p>ChaCha20-Poly1305 allows no parameters; hence the main part here is really just the keys.
However, Tink allows prefixing every ciphertext with an ID-dependent prefix, see {@link
ChaCha20Poly1305Parameters.Variant}.
java_src/src/main/java/com/google/crypto/tink/aead/ChaCha20Poly1305Key.java