@Override
    public Set<Entry<String, String>> entrySet() {
        final Set<Entry<String, String>> rtnSet = new HashSet<>();
        for (final Entry<CIString, String> entry : map.entrySet()) {
            rtnSet.add(new CIEntryAdaptor(entry));
        }
        return rtnSet;
    }
DOESN'T adhere to the contract of {@link Map#entrySet()}, so any changes
to the returned {@link Set} will NOT affect this map.
stroom-meta/stroom-meta-api/src/main/java/stroom/meta/api/CIStringHashMap.java