readFeatureCollectionMetadata(source) {
    if (!source) {
      return undefined;
    }
    if (typeof source === 'string') {
      const doc = parse(source);
      return this.readFeatureCollectionMetadataFromDocument(doc);
    }
    if (isDocument(source)) {
      return this.readFeatureCollectionMetadataFromDocument(
        /** @type {Document} */ (source),
      );
    }
    return this.readFeatureCollectionMetadataFromNode(
      /** @type {Element} */ (source),
    );
  }
Read feature collection metadata of the source.

@param {Document|Element|Object|string} source Source.
@return {FeatureCollectionMetadata|undefined}
    FeatureCollection metadata.
@api