@Override
    public int compareTo(FieldValue fieldValue) {
        int comp = super.compareTo(fieldValue);

        if (comp != 0) {
            return comp;
        }

        //types are equal, this must be of this type
        Array otherValue = (Array) fieldValue;
        return CollectionComparator.compare(values, otherValue.values);
    }
This wrapper class is used to wrap a list that isn't a list of field
values. This is done, as to not alter behaviour from previous state,
where people could add whatever list to a document, and then keep adding
stuff to the list afterwards.

<p>
TODO: Remove this class and only allow instance of Array to be added.
document/src/main/java/com/yahoo/document/datatypes/Array.java