::deep selector is unknown pseudo selector in blazor application using Rider Jetbrains

I am trying to make css isolation for Blazors QuickGrid component. When I use the pseudo selector "::deep" it gives we the warning: " Unknown pseudo selector 'deep'".How can I fix this and is it possible when using Rider Jetbrains IDE?

::deep th.country-name { width: 14rem; }/* Subtle stripe effect */ ::deep tr:nth-child(even) {    background: rgba(255,255,255,0.4);}/* Don't collapse rows even if they are empty */::deep tbody tr { height: 1.8rem; }```