presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/util/SynchronizedResultIterator.java/SynchronizedResultIterator/SynchronizedResultIterator
class SynchronizedResultIterator:    public SynchronizedResultIterator(ResultIterator<T> iterator)
    {
        this.iterator = requireNonNull(iterator, "iterator is null");
    }