@Override
    public Page<T,R> next() {
        if (page == null) {
            page = col.firstPage();
        } else {
            page = page.nextPage();
            col.setLastLowLevelResult(page.getLowLevelResult());
        }
        return page;
    }
@param <T> resource type
@param <R> low level result type
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/document/internal/PageIterator.java