Plugin custom styles file not loaded in plugin configure view.

I am trying to add custom sytles in my custom plugin configure page but they are not loaded however when inspect I the source code I see that the my custom styles file is linked in the head tag. Below is my code in view. Am I missing something?

@{
//Plugin Custom CSS file
Html.AddCssFileParts(ResourceLocation.Head, "~/Plugins/Widgets.CarpartFinder/Content/CarpartCustom.css");
}