code: func (m *HoltLinearMovAvgModel) Alpha(alpha float64) *HoltLinearMovAvgModel {
  	m.alpha = &alpha
  	return m
  }
docs: // Alpha controls the smoothing of the data. Alpha = 1 retains no memory
  // of past values (e.g. a random walk), while alpha = 0 retains infinite
  // memory of past values (e.g. the series mean). Useful values are somewhere
  // in between. Defaults to 0.5.