protected virtual void ParseSelectorCombineOperator(ItemFactory itemFactory, ITextProvider text, TokenStream tokens)
 {
     if (IdReferenceOperator.IsAtIdReferenceOperator(tokens))
     {
         ParseItem combineOperator = itemFactory.Create <IdReferenceOperator>(this);
         if (combineOperator.Parse(itemFactory, text, tokens))
         {
             SelectorCombineOperator = combineOperator;
             Children.Add(combineOperator);
         }
     }
     else
     {
         SelectorCombineOperator = Children.AddCurrentAndAdvance(tokens, CssClassifierContextType.SelectorCombineOperator);
     }
 }
 protected virtual bool IsAtSelectorCombineOperator(ITextProvider text, TokenStream tokens)
 {
     return(tokens.CurrentToken.IsSimpleSelectorCombineOperator() ||
            IdReferenceOperator.IsAtIdReferenceOperator(tokens));
 }