@cache_readonly
    def _var_beta_raw(self):
        """Returns the raw covariance of beta."""
        x = self._x
        y = self._y

        dates = x.index.levels[0]

        cluster_axis = None
        if self._cluster == 'time':
            cluster_axis = 0
        elif self._cluster == 'entity':
            cluster_axis = 1

        nobs = self._nobs
        rmse = self._rmse_raw
        beta = self._beta_raw
        df = self._df_raw
        window = self._window

        if not self._time_effects:
            # Non-transformed X
            cum_xx = self._cum_xx(x)

        results = []
        for n, i in enumerate(self._valid_indices):
            if self._is_rolling and i >= window:
                prior_date = dates[i - window + 1]
            else:
                prior_date = dates[0]

            date = dates[i]

            x_slice = x.truncate(prior_date, date)
            y_slice = y.truncate(prior_date, date)

            if self._time_effects:
                xx = _xx_time_effects(x_slice, y_slice)
            else:
                xx = cum_xx[i]
                if self._is_rolling and window >= i:
                    xx = xx - cum_xx[i - window]

            result = _var_beta_panel(y_slice, x_slice, beta[n], xx, rmse[n],
                                     cluster_axis, self._nw_lags,
                                     nobs[n], df[n], self._nw_overlap)

            results.append(result)

        return np.array(results)
dataset/ETHPy150Open pydata/pandas/pandas/stats/plm.py/MovingPanelOLS._var_beta_raw/swapped operands of `>=`