Returns likelihood of the states given the variance latent variables

        Parameters
        ----------
        beta : np.array
            Contains untransformed starting values for latent variables
        alpha : np.array
            State matrix
        
        Returns
        ----------
        State likelihood

def state_likelihood(self, beta, alpha):
        """ Returns likelihood of the states given the variance latent variables

        Parameters
        ----------
        beta : np.array
            Contains untransformed starting values for latent variables
        alpha : np.array
            State matrix
        
        Returns
        ----------
        State likelihood
        """
        _, _, _, Q = self._ss_matrices(beta)
        residuals = alpha[0][1:]-alpha[0][:-1]
        return np.sum(ss.norm.logpdf(residuals, loc=0, scale=np.power(Q.ravel(),0.5)))