readFeatureCollectionMetadataFromDocument(doc) {
    for (let n = /** @type {Node} */ (doc.firstChild); n; n = n.nextSibling) {
      if (n.nodeType == Node.ELEMENT_NODE) {
        return this.readFeatureCollectionMetadataFromNode(
          /** @type {Element} */ (n),
        );
      }
    }
    return undefined;
  }
@param {Document} doc Document.
@return {FeatureCollectionMetadata|undefined}
    FeatureCollection metadata.