code: @SuppressWarnings("unchecked")
    public static <E extends Enum<E> & NumberedValue> Option<E> valueOf(final Class<E> type, int number) {
      checkNotNull(type);
      E value = (E) mappings.getUnchecked(type).get(number);
      return Option.of(value);
    }
docs: Returns the enum constant of the specified enum type with the specified
  number. (This function is similar to {@link Enum#valueOf(Class, String)}.)
  
  @throws NullPointerException if the {@code value} is {@code null}