code: func (mb *MetricBatcher) BatchAddCounter(name string, delta uint64) {
  	mb.lock.Lock()
  	defer mb.lock.Unlock()
  
  	if mb.closed {
  		panic("Attempting to send metrics after closed")
  	}
  
  	mb.add(batch{name: name, value: delta})
  }
docs: // BatchAddCounter increments the named counter by the provided delta, but does not
  // immediately send a CounterEvent.