public override void ToCss(TextWriter writer, IStyleFormatter formatter)
        {
            var rules = formatter.BlockRules(Rules);

            writer.Write(formatter.Rule(RuleNames.Keyframes, _name, rules));
        }
        public override void ToCss(TextWriter writer, IStyleFormatter formatter)
        {
            var rules = formatter.BlockRules(Rules);

            writer.Write(formatter.Rule(RuleNames.Supports, ConditionText, rules));
        }
        public override void ToCss(TextWriter writer, IStyleFormatter formatter)
        {
            var rules = formatter.BlockRules(_style);

            writer.Write(formatter.Rule(RuleNames.Page, SelectorText, rules));
        }