code: func (hg *Histogram) Copy() *Histogram {
  	newHist := *hg
  	newHist.Bounds = hg.Bounds.CopyConstruct()
  	newHist.Buckets = make([]Bucket, 0, len(hg.Buckets))
  	for _, bkt := range hg.Buckets {
  		newHist.Buckets = append(newHist.Buckets, bkt)
  	}
  	return &newHist
  }
docs: // Copy deep copies the histogram.