def holtWintersAberration(requestContext, seriesList, delta=3):
    """
    Performs a Holt-Winters forecast using the series as input data and plots
    the positive or negative deviation of the series data from the forecast.
    """
    results = []
    for series in seriesList:
        confidenceBands = holtWintersConfidenceBands(requestContext, [series],
                                                     delta)
        lowerBand = confidenceBands[0]
        upperBand = confidenceBands[1]
        aberration = list()
        for i, actual in enumerate(series):
            if actual is None:
                aberration.append(0)
            elif upperBand[i] is not None and actual > upperBand[i]:
                aberration.append(actual - upperBand[i])
            elif lowerBand[i] is not None and actual < lowerBand[i]:
                aberration.append(actual - lowerBand[i])
            else:
                aberration.append(0)

        newName = "holtWintersAberration(%s)" % series.name
        results.append(TimeSeries(newName, series.start, series.end,
                                  series.step, aberration))
    return results

    Performs a Holt-Winters forecast using the series as input data and plots
    the positive or negative deviation of the series data from the forecast.
    
graphite_api/functions.py