def _plot_ci_bars(ax, x, central_data, ci, color, err_kws, **kwargs):
    """Plot error bars at each data point."""
    for x_i, y_i, (low, high) in zip(x, central_data, ci.T):
        ax.plot([x_i, x_i], [low, high], color=color, solid_capstyle=
            'round', **err_kws)
