readTransactionResponseFromDocument(doc) {
    for (let n = /** @type {Node} */ (doc.firstChild); n; n = n.nextSibling) {
      if (n.nodeType == Node.ELEMENT_NODE) {
        return this.readTransactionResponseFromNode(/** @type {Element} */ (n));
      }
    }
    return undefined;
  }
@param {Document} doc Document.
@return {TransactionResponse|undefined} Transaction response.