default CodeBlock newIdentifier(String prefix) {
    throw new UnsupportedOperationException();
  }
Returns an identifier beginning with the given prefix and that is distinct from any identifier
returned by another call to this method. The returned identifier will contain a {@code $},
which should also mean it is distinct from identifiers in user code that are in scope.

<p>The default implementation of this method throws {@link UnsupportedOperationException} for
compatibility reasons.
value/src/main/java/com/google/auto/value/extension/serializable/serializer/interfaces/SerializerFactory.java