code: func (ms *MetricSender) AddToCounter(name string, delta uint64) error {
  	return ms.eventEmitter.Emit(&events.CounterEvent{Name: &name, Delta: &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.