presto-main/src/main/java/io/prestosql/operator/NestedLoopJoinPagesSupplier.java/NestedLoopJoinPagesSupplier/getPagesFuture
class NestedLoopJoinPagesSupplier:    @Override
    public ListenableFuture<NestedLoopJoinPages> getPagesFuture()
    {
        return transformAsync(pagesFuture, Futures::immediateFuture, directExecutor());
    }