Creates model latent variables

        Returns
        ----------
        None (changes model attributes)

def _create_latent_variables(self):
        """ Creates model latent variables

        Returns
        ----------
        None (changes model attributes)
        """

        for ar_term in range(self.ar):
            self.latent_variables.add_z('AR(' + str(ar_term+1) + ')', fam.Normal(0,0.5,transform=None), fam.Normal(0,3))

        for sc_term in range(self.sc):
            self.latent_variables.add_z('SC(' + str(sc_term+1) + ')', fam.Normal(0,0.5,transform=None), fam.Normal(0,3))

        for parm in range(len(self.X_names)):
            self.latent_variables.add_z('Beta ' + self.X_names[parm], fam.Normal(0,3,transform=None), fam.Normal(0,3))