Creates forecasted states and variances

        Parameters
        ----------
        beta : np.ndarray
            Contains untransformed starting values for latent variables

        Returns
        ----------
        a : np.ndarray
            Forecasted states

        P : np.ndarray
            Variance of forecasted states

def _forecast_model(self,beta,h):
        """ Creates forecasted states and variances

        Parameters
        ----------
        beta : np.ndarray
            Contains untransformed starting values for latent variables

        Returns
        ----------
        a : np.ndarray
            Forecasted states

        P : np.ndarray
            Variance of forecasted states
        """     

        T, Z, R, Q, H = self._ss_matrices(beta)
        return univariate_kalman_fcst(self.data,Z,H,T,Q,R,0.0,h)