public ListIterator<DataTypeName> inheritedIterator() {
        List<DataTypeName> names = new ArrayList<>(inherits.size());
        for (DocumentType type : inherits) {
            names.add(type.getDataTypeName());
        }
        return List.copyOf(names).listIterator();
    }
Returns the DocumentNames which are directly inherited by this
as a read-only collection.
If this document type does not explicitly inherit anything, the list will
contain the root type 'Document'

@return a read-only list iterator containing the name Strings of the directly
        inherited document types of this
document/src/main/java/com/yahoo/document/DocumentType.java