code: func NewFactory(buckets int) metrics.Factory {
  	return adapters.WrapFactoryWithoutTags(
  		&factory{
  			factory: expvar.NewFactory(buckets),
  		},
  		adapters.Options{},
  	)
  }
docs: // NewFactory creates a new metrics factory using go-kit expvar package.
  // buckets is the number of buckets to be used in histograms.