Method removeAllFeatures

src/openlayers/overlay/Graph.js:405–408

* @function Graph.prototype.removeAllFeatures * @description 移除所有的要素。

()

     * @description  移除所有的要素。
     */
    removeAllFeatures() {
        this.clearCache();
        super.removeAllFeatures();
    }

    /**
     * @function Graph.prototype.redraw