code: public void setHistoricalAdjustment(com.google.api.ads.admanager.axis.v201902.HistoricalAdjustment historicalAdjustment) {
          this.historicalAdjustment = historicalAdjustment;
      }
docs: Sets the historicalAdjustment value for this TrafficForecastAdjustmentSegment.
  
  @param historicalAdjustment   * The content of the adjustment which references historical data.
  This field should be set if
  {@code basisType} is {@link BasisType.HISTORICAL}
  and null if {@link BasisType.ABSOLUTE}.