code: def _se_all(self):
          
          err = np.expand_dims(self._ms_err, axis=1)
          t1 = np.diagonal(
              np.linalg.inv(np.matmul(self.xwins.swapaxes(1, 2), self.xwins)),
              axis1=1,
              axis2=2,
          )
          return np.squeeze(np.sqrt(t1 * err))
docs: Standard errors (SE) for all parameters, including the intercept.