code: func AddToCounter(name string, delta uint64) error {
  	if metricSender == nil {
  		return nil
  	}
  	return metricSender.AddToCounter(name, delta)
  }
docs: // AddToCounter sends an event to increment the named counter by the specified
  // (positive) delta. Maintaining the value of the counter is the responsibility
  // of the receiver, as with IncrementCounter.