public Map.Entry<Field, FieldValue> next() {
            if (position >= increasing.length) {
                throw new NoSuchElementException("No more elements in collection");
            }
            return new FieldEntry(increasing[position++]);
        }
Clears this and assigns from the given {@link StructuredFieldValue}
document/src/main/java/com/yahoo/document/datatypes/Struct.java