handleSourceFeatureAdded_(event) {
    const feature = event.feature;
    const geometry = feature.getGeometry();
    if (geometry && geometry.getType() === 'Point') {
      this.featureCache_[getUid(feature)] = {
        feature: /** @type {PointFeature} */ (feature),
        properties: feature.getProperties(),
        flatCoordinates: /** @type {Point} */ (geometry).getFlatCoordinates(),
      };
      this.featureCount_++;
    }
  }
@param {import("../../source/Vector.js").VectorSourceEvent} event Event.
@private