docs: public static HistogramAggregationIterator create(final List<HistogramSpan> spans, 
                                                      final long start_time,
                                                      final long end_time, 
                                                      final HistogramAggregation aggregation, 
                                                      final DownsamplingSpecification downsampler,
                                                      final long query_start, 
                                                      final long query_end, 
                                                      final boolean is_rollup) {
      final int size = spans.size();
      final HistogramSeekableView[] iterators = new HistogramSeekableView[size];
      for (int i = 0; i < size; i++) {
        HistogramSeekableView it;
        if (downsampler == DownsamplingSpecification.NO_DOWNSAMPLER) {
          it = spans.get(i).spanIterator();
        } else {
          it = spans.get(i).downsampler(start_time, end_time, downsampler, 
              is_rollup, query_start, query_end);
        }
        iterators[i] = it;
      }
      return new HistogramAggregationIterator(iterators, start_time, 
          end_time, aggregation);
    }