code: def generic_model(cls, site_class, **kwds):
          
          p = dict(cls.PARAMS[site_class])
          p.update(kwds)
          return cls(**p)
docs: Use generic model parameters based on site class.
  
          Parameters
          ----------
          site_class: str
              Site classification. Possible options are:
               * Geomatrix AB
               * Geomatrix CD
               * USGS AB
               * USGS CD
               * USGS A
               * USGS B
               * USGS C
               * USGS D
  
              See the report for definitions of the Geomatrix site
              classication. USGS site classification is based on :math:`V_{s30}`:
  
              =========== =====================
              Site Class  :math:`V_{s30}` (m/s)
              =========== =====================
              A           >750 m/s
              B           360 to 750 m/s
              C           180 to 360 m/s
              D           <180 m/s
              =========== =====================
  
          Returns
          -------
          ToroVelocityVariation
              Initialized :class:`ToroVelocityVariation` with generic parameters.