code: def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
          
          mean, stddevs = super().get_mean_and_stddevs(
              sites, rup, dists, imt, stddev_types)
  
          idx_rock = sites.vs30 >= self.ROCK_VS30
          idx_soil = sites.vs30 < self.ROCK_VS30
  
          mean[idx_rock] += 0.275
          mean[idx_soil] += 0.31
  
          return mean, stddevs
docs: See :meth:`superclass method
          <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
          for spec of input and result values.