addFeatureInternal(feature) {
    const featureKey = getUid(feature);

    if (!this.addToIndex_(featureKey, feature)) {
      if (this.featuresCollection_) {
        this.featuresCollection_.remove(feature);
      }
      return;
    }

    this.setupChangeEvents_(featureKey, feature);

    const geometry = feature.getGeometry();
    if (geometry) {
      const extent = geometry.getExtent();
      if (this.featuresRtree_) {
        this.featuresRtree_.insert(extent, feature);
      }
    } else {
      this.nullGeometryFeatures_[featureKey] = feature;
    }

    this.dispatchEvent(
      new VectorSourceEvent(VectorEventType.ADDFEATURE, feature),
    );
  }
Add a feature without firing a `change` event.
@param {FeatureType} feature Feature.
@protected