rue});
      iframe.src = testURI(&quot;resource&quot;, &quot;page&quot;, key);
    })

read: async (key) =&gt; {
      let iframe = document.createElement(&quot;iframe&quot;);
      document.body.appendChild(iframe);
      let iframeLoadPromise = new Promise((resolve, reject) =&gt; {
        iframe.addEventListener(&quot;load&quot;, resolve, {once: true});
      });
      let address = testURI(&quot;resource&quot;, &quot;page&quot;, key);
      iframe.src = address;
      await iframeLoadPromise;
      let