public static EffectiveMetaSet singleton(final EffectiveMeta effectiveMeta) {
        Objects.requireNonNull(effectiveMeta);
        return new Builder(effectiveMeta.getFeedName(), effectiveMeta.getTypeName())
                .add(effectiveMeta)
                .build();
    }
Cache the hash code as we are pretty much guaranteed to call hashCode in
EffectiveStreamInternPool
stroom-meta/stroom-meta-api/src/main/java/stroom/meta/api/EffectiveMetaSet.java