if filter == nil {
		return nil, nil
	}

	gToIntervals := make(map[trace.GoID][]interval)
	for _, g := range t.summary.Goroutines {
		for _, r := range g.Regions {
			if !filter.match(t, r) {
				continue
			}
			gToIntervals[g.ID] = append(gToIntervals[g.ID], regionInterval(t, r))
		}
	}

	for g, intervals := range gToIntervals {
		// In order to remove nested regions and