static <T> Optional<T> unwrapOptionalEquivalence(
      Optional<Equivalence.Wrapper<T>> wrappedOptional) {
    return wrappedOptional.map(Equivalence.Wrapper::get);
  }
Unwraps an {@link Optional} of a {@link Equivalence.Wrapper} into an {@code Optional} of the
underlying type.
factory/src/main/java/com/google/auto/factory/processor/Mirrors.java