be width="480" height="270"
               video-id="9bZkp7q19f0">
  </amp-youtube>
  <!-- This is the current way to do it, according to
https://github.com/ampproject/amphtml/blob/main/extensions/amp-youtube/amp-youtube.md -->
  <amp-youtube width="480" height="270"
               data-videoid="https://www.youtube.com/watch?v=dQw4w9WgXcQ">
  </amp-youtube>
  <!-- This is invalid, the video id is missing. -->
  <amp-youtube width="480" height="270"></amp-youtube>
  <!-- This is also invalid, dimensions are 