code: def shear_vel_at_depth(self, y_c):
          
          sl = self.get_soil_at_depth(y_c)
          if y_c <= self.gwl:
              saturation = False
          else:
              saturation = True
          if hasattr(sl, "get_shear_vel_at_v_eff_stress"):
              v_eff = self.get_v_eff_stress_at_depth(y_c)
              vs = sl.get_shear_vel_at_v_eff_stress(v_eff, saturation)
          else:
              vs = sl.get_shear_vel(saturation)
          return vs
docs: Get the shear wave velocity at a depth.
  
          :param y_c: float, depth from surface
          :return: