public override LessNode VisitKeyframe(LessParser.KeyframeContext context)
        {
            var expressions = context.singleValuedExpression().Select(GetSingleValuedExpression);

            var block = (RuleBlock)context.block().Accept(this);

            return(new Keyframe(expressions, block));
        }
 public virtual LessNode VisitKeyframe(LessParser.KeyframeContext context)
 {
     throw new System.NotImplementedException();
 }