Server Error when use theme inheritance

[akhyarrh]

Ref.: https://getgrav.org/blog/theme-development-with-inheritance

Based on that post I setup inheritance:

streams:
 schemes:
   theme:
     type: ReadOnlyStream
     prefixes:
       '':
         - user/themes/mytheme
         - user/themes/cacti

pages:
 theme: mytheme

Run php -S localhost:8000 system/router.php , go to http://localhost:8000/,throw 400 - Template "post-list.html.twig" is not defined.