@Override
  public String toString() {
    return String.format(
        "(typeUrl=%s, outputPrefixType=%s)",
        serialization.getKeyTemplate().getTypeUrl(),
        outputPrefixToString(serialization.getKeyTemplate().getOutputPrefixType()));
  }
returns the serialization which was used to create this object.
java_src/src/main/java/com/google/crypto/tink/internal/LegacyProtoParameters.java