code: def vi_return_param(self, index):
          
          if index == 0:
              return self.mu0
          elif index == 1:
              return np.log(self.sigma0)
docs: Wrapper function for selecting appropriate latent variable for variational inference
  
          Parameters
          ----------
          index : int
              0 or 1 depending on which latent variable
  
          Returns
          ----------
          The appropriate indexed parameter