blazor toast service from where i have this .toast:not(.show)

im boulding in blazor some webappfound this tutorial about toast service - preaty basic stuffhttps://www.gushiciku.cn/pl/2CEB

i did everything as in this tutorial and it was not workingi was searching whyand found that as on screen from some place - please tell me what

on build it is adding

.toast:not(.show) {display: none;

}

as on screenshot

when i remove this markup it is working finefrom where it is comming from ? i does not have this in any css etc , tryied to gogole but no luck...

thanks and regards !

-------- editi added show to @(IsVisible ? "show toast-visible" : null) and it works fine but im not sure it it is best solution ?

the issue is bootstrap 4/5 related. does anyone have similar solution using bootstrap 5 ands it toast component ?:)

regards once more.