@Nullable
 public static PsiElement resolveMixin(@NotNull PsiElement base, @NotNull String name) {
   CssResolveProcessor processor = CssPluginsFacade.getMixinProcessor(base, name);
   if (processor.executeInScope(base)) {
     processFile(
         base.getContainingFile(),
         processor,
         ResolveState.initial().put(PROCESSED_PATHS, new HashSet<String>()));
   }
   return processor.getResult();
 }