public int previousIndex() {
                    return it.previousIndex();
                }
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