how to get an iframe in document.write

i have tried this:

<script>
  function aboutblank(){
  let win = window.open();
  win.document.write("<iframe src="/Offline_Download_Version.html"></iframe>")}
                     </script> 

<button onclick="aboutblank()">Click me</button>

but it didnt work, ive also tried putting the actual file url, the plain code url, the plain code, and a few more things, but i cant figure it out.

i am trying to put home-schoology.github.io/Offline_Download_Version.html into this script in an iframe, so how would i go along doing this? (it is supposed to open in an about:blank tab and open an iframe with the html)