if (this.backgroundRangeMarkers != null) {
            Collection markers
                = (Collection) this.backgroundRangeMarkers.get(key);
            if (markers != null) {
                Iterator iterator = markers.iterator();
                while (iterator.hasNext()) {
                    Marker m = (Marker) iterator.next();
                    m.removeChangeListener(this);
                }
                markers.clear();