n mergeBins_(x, y) {
    x.sum += y.sum;
    const allBins = [...x.bins, ...y.bins];
    allBins.sort((a, b) => a.min - b.min);
    x.bins = [];
    let last = undefined;
    for (const bin of allBins) {
      if (last !== undefined && bin.min === last.min) {
        if (last.max !== bin.max) throw new Error('Incompatible bins');
        if (bin.count === 0) continue;
        last.count += bin.count;
        for (const event of bin.events) {
          last.events.add(event);
        }
        last.processes