code: func shouldDropMetricName(op ItemType) bool {
  	switch op {
  	case ItemADD, ItemSUB, ItemDIV, ItemMUL, ItemPOW, ItemMOD:
  		return true
  	default:
  		return false
  	}
  }
docs: // shouldDropMetricName returns whether the metric name should be dropped in the
  // result of the op operation.