setLayerGroup(layerGroup) {
    const oldLayerGroup = this.getLayerGroup();
    if (oldLayerGroup) {
      this.handleLayerRemove_(new GroupEvent('removelayer', oldLayerGroup));
    }
    this.set(MapProperty.LAYERGROUP, layerGroup);
  }
Sets the layergroup of this map.
@param {LayerGroup} layerGroup A layer group containing the layers in this map.
@observable
@api