code: func BandwidthSilverman(data interface {
  	StdDev() float64
  	Weight() float64
  }) float64 {
  	return 1.06 * data.StdDev() * math.Pow(data.Weight(), -1.0/5)
  }
docs: // BandwidthSilverman is a bandwidth estimator implementing
  // Silverman's Rule of Thumb. It's fast, but not very robust to
  // outliers as it assumes data is approximately normal.
  //
  // Silverman, B. W. (1986) Density Estimation.