code: func GetOrRegisterMeter(name string, r Registry) Meter {
  	if nil == r {
  		r = DefaultRegistry
  	}
  	return r.GetOrRegister(name, NewMeter).(Meter)
  }
docs: // GetOrRegisterMeter returns an existing Meter or constructs and registers a
  // new StandardMeter.
  // Be sure to unregister the meter from the registry once it is of no use to
  // allow for garbage collection.