code: def vi_score(self, x, index):
          
          if index == 0:
              return self.vi_loc_score(x)
          elif index == 1:
              return self.vi_scale_score(x)
docs: Wrapper function for selecting appropriate score
  
          Parameters
          ----------
          x : float
              A random variable
  
          index : int
              0 or 1 depending on which latent variable
  
          Returns
          ----------
          The gradient of the scale latent variable at x