@JsonIgnore
    public Optional<PropertyPath> getParent() {
        if (parentParts.isEmpty()) {
            return Optional.empty();
        } else {
            return Optional.of(new PropertyPath(parentParts));
        }
    }
Merge parts onto the end of this and return a new {@link PropertyPath}
stroom-util-shared/src/main/java/stroom/util/shared/PropertyPath.java