readFeaturesFromDocument(doc, options) {
    /** @type {Array<import("../Feature.js").default>} */
    const features = [];
    for (let n = doc.firstChild; n; n = n.nextSibling) {
      if (n.nodeType == Node.ELEMENT_NODE) {
        extend(
          features,
          this.readFeaturesFromNode(/** @type {Element} */ (n), options),
        );
      }
    }
    return features;
  }
@param {Document} doc Document.
@param {import("./Feature.js").ReadOptions} [options] Options.
@protected
@return {Array<import("../Feature.js").default>} Features.