public HnswIndexParams overrideFrom(Optional<HnswIndexParams> other) {
        if (! other.isPresent()) return this;
        HnswIndexParams rhs = other.get();
        return new HnswIndexParams(rhs.maxLinksPerNode.or(() ->  maxLinksPerNode),
                rhs.neighborsToExploreAtInsert.or(() ->  neighborsToExploreAtInsert),
                rhs.multiThreadedIndexing.or(() -> multiThreadedIndexing));
    }
Creates a new instance where values from the given parameter instance are used where they are present,
otherwise we use values from this.
config-model/src/main/java/com/yahoo/schema/document/HnswIndexParams.java