old_contents: class Radial1DModel(object):
      def __init__(self, velocity, density, abundance, t_rad,
                   v_boundary_inner, v_boundary_outer, w=None):
          self.velocity = velocity
          self.density = density
          self.abundance = abundance
          self.t_rad = t_rad
          self.v_boundary_inner = v_boundary_inner
          self.v_boundary_outer = v_boundary_outer
          self.w = w
  
      @classmethod
      def from_config(cls, config):
          pass
  
new_contents: import numpy as np
  
  
  class Radial1DModel(object):
      def __init__(self, velocity, density, abundance, t_inner, t_radiative,
                   v_boundary_inner, v_boundary_outer, time_explosion,
                   dilution_factor=None):
          self.velocity = velocity
          self.density = density
          self.abundance = abundance
          self.t_inner = t_inner
          self.t_radiative = t_radiative
          self.v_boundary_inner = v_boundary_inner
          self.v_boundary_outer = v_boundary_outer
          self.time_explosion = time_explosion
          if dilution_factor is None:
              self.dilution_factor = 0.5 * (1 - np.sqrt(
                  1 - (self.r_inner[0] ** 2 / self.r_middle ** 2).to(1).value))
          else:
              self.dilution_factor = dilution_factor
  
      @property
      def w(self):
          return self.dilution_factor
  
      @w.setter
      def w(self, value):
          self.dilution_factor = value
  
      @property
      def t_rad(self):
          return self.t_radiative
  
      @t_rad.setter
      def t_rad(self, value):
          self.t_radiative = value
  
      @property
      def r_inner(self):
          return self.time_explosion * self.v_inner
  
      @property
      def r_outer(self):
          return self.time_explosion * self.v_outer
  
      @property
      def r_middle(self):
          return 0.5 * self.r_inner + 0.5 * self.r_outer
  
      @property
      def v_inner(self):
          return self.velocity[:-1]
  
      @property
      def v_outer(self):
          return self.velocity[1:]
  
      @property
      def v_middle(self):
          return 0.5 * self.v_inner + 0.5 * self.v_outer
  
      @classmethod
      def from_config(cls, config):
          pass
  
subject: Introduce the basics of the new model/base.py.