@Override
    public Object clone() {
        try {
            Index copy = (Index)super.clone();
            copy.aliases = new LinkedHashSet<>(this.aliases);
            return copy;
        }
        catch (CloneNotSupportedException e) {
            throw new RuntimeException("Programming error",e);
        }
    }
Makes a deep copy of this index
config-model/src/main/java/com/yahoo/schema/Index.java