public DocPath append(final String otherPart) {
        if (otherPart == null || otherPart.isEmpty()) {
            return this;
        } else {
            return new DocPath(this.getParts(), otherPart, absolute);
        }
    }
Append part onto the end of this and return a new {@link DocPath}
stroom-util-shared/src/main/java/stroom/util/shared/DocPath.java