code: func (a *AggMetric) gcAggregators(now, chunkMinTs, metricMinTs uint32) (uint32, bool) {
  	var points uint32
  	stale := true
  	for _, agg := range a.aggregators {
  		p, s := agg.GC(now, chunkMinTs, metricMinTs, a.lastWrite)
  		points += p
  		stale = stale && s
  	}
  	return points, stale
  }
docs: // gcAggregators returns whether all aggregators are stale and can be removed, and their pointcount if so