public override string ToString()
        {
            var tag = new CollapsibleTag(_id, _title);
            tag.AppendContent(_content().ToString());

            return tag.ToString();
        }
        // SAMPLE: UsingCollapsibleTag
        public CollapsiblePartialViewModel get_collapsible_partial()
        {
            var inner = new HtmlTag("div");
            for (var i = 0; i < 5; i++ )
            {
                inner.Add("p").Text(Guid.NewGuid().ToString());
            }


            var tag = new CollapsibleTag("acc1", "This is the collapsible tag");
            tag.AppendContent(inner.ToString());

            return new CollapsiblePartialViewModel{
                Tag = tag
            };
        }