code: def smoothed_state(self,data,beta):
                   
  
          T, Z, R, Q, H = self._ss_matrices(beta)
          alpha, V = univariate_KFS(data,Z,H,T,Q,R,0.0)
          return alpha, V
docs: Creates the negative log marginal likelihood of the model
  
          Parameters
          ----------
  
          data : np.array
              Data to be smoothed
  
          beta : np.array
              Contains untransformed starting values for latent variables
  
          Returns
          ----------
          - Smoothed states