@Override
    public int hashCode() {
        if (hashcode == 0) {
            hashcode = Objects.hashCode(uniqueKey);
        }
        return hashcode;
    }
@return True if this node's set of {@link NodeFlag}s is missing ALL the flags in nodeFlags.
stroom-core-shared/src/main/java/stroom/explorer/shared/ExplorerNode.java