@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 PrfKey getPrfKey() {
    return prfKey;
  }
Represents a Derivation key which is based on a PRF.

<p>An object of this class represents the map which 1) uses the given PRF (as specified by {@link
#getPrfKey}) to get sufficient key material from the salt, then 2) creates a key for the
parameters as specified in {@code getParameters().getDerivedKeyParameters()}.
java_src/src/main/java/com/google/crypto/tink/keyderivation/PrfBasedKeyDerivationKey.java