== should format at rule custom-media ==
@custom-media --narrow-window (max-width: 30em);
@custom-media --phone (width < 480px) and (--portrait);
@custom-media --sm-viewport only screen and (min-width: 576px);

[expect]
@custom-media --narrow-window (max-width: 30em);

@custom-media --phone (width < 480px) and (--portrait);

@custom-media --sm-viewport only screen and (min-width: 576px);