code: func (a *SerialDiffAggregation) Lag(lag int) *SerialDiffAggregation {
  	a.lag = &lag
  	return a
  }
docs: // Lag specifies the historical bucket to subtract from the current value.
  // E.g. a lag of 7 will subtract the current value from the value 7 buckets
  // ago. Lag must be a positive, non-zero integer.