/// <summary>
        /// Create importantComment Nodes
        /// </summary>
        /// <param name="commonTree"> the parent of list of the comment trees</param>
        /// <returns>The list of comment nodes</returns>
        private static ReadOnlyCollection <ImportantCommentNode> CreateImportantCommentNodes(CommonTree commonTree)
        {
            Contract.Requires(!commonTree.Equals(null));
            List <ImportantCommentNode> comments = new List <ImportantCommentNode>();

            foreach (var child in commonTree.Children)
            {
                if (child.Type.Equals(CssParser.IMPORTANT_COMMENTS))
                {
                    comments.Add(new ImportantCommentNode(child.Text));
                }
            }

            return(comments.AsReadOnly());
        }