public LegendItemCollection getFixedLegendItems() {
        return this.fixedLegendItems;
    }

    /**
     * Sets the fixed legend items for the plot.  Leave this set to
     * <code>null</code> if you prefer the legend items to be created
     * automatically.
     *
     * @param items  the legend items (<code>null</code> permitted).
     *
     * @see #getFixedLegendItems()
     */
    public void setFixedLegendItems(LegendItemCollection items) {
        this.fixedLegendItems = items;
        fireChangeEvent();