code: def _create_latent_variables(self):
          
  
          self.latent_variables.add_z('Sigma^2 irregular', fam.Flat(transform='exp'), fam.Normal(0,3))
  
          self.latent_variables.add_z('Constant', fam.Flat(transform=None), fam.Normal(0,3))
  
          for parm in range(1,self.ar+1):
              self.latent_variables.add_z('Sigma^2 AR(' + str(parm) + ')', fam.Flat(transform='exp'), fam.Normal(0,3))
docs: Creates model latent variables
  
          Returns
          ----------
          None (changes model attributes)