def _plot_ci_band(ax, x, ci, color, err_kws, **kwargs):
    """Plot translucent error bands around the central tendancy."""
    low, high = ci
    if 'alpha' not in err_kws:
        err_kws['alpha'] = 0.2
    ax.fill_between(x, low, high, facecolor=color, **err_kws)
