custom elements that use extends

[nosovk]

We can create web-components using svelte. But in documentation mostly covered case with new custom-tag.
I can't understand hot to use extends.

customElements.define("custom-video", videoComponent, { extends: "video" });

for example if I want to extend

<svelte:options tag={null}>

to disable automatic registration of a web-component.
That I should be able to register my component manually with "extends" param.
But when I will do registration manually - it will fail, because component should be inherited from HTMLVideoElement, which is don't.
Is there some doc or example how to extend existing tags with svelte?