code: def _alpha(self, L):
               
          return la.cho_solve((L.T, True), la.cho_solve((L, True), np.transpose(self.data)))
docs: Covariance-derived term to construct expectations. See Rasmussen & Williams.
          
          Parameters
          ----------
          L : np.ndarray
              Cholesky triangular
  
          Returns
          ----------
          np.ndarray (alpha)