private static async Task WriteInlineCategoriesContentAsync(XmlWriter writer, InlineCategoriesDocument categories, string version)
        {
            writer = XmlWriterWrapper.CreateFromWriter(writer);
            if (!string.IsNullOrEmpty(categories.Scheme))
            {
                await writer.WriteAttributeStringAsync(Atom10Constants.SchemeTag, categories.Scheme);
            }
            // by default, categories are not fixed
            if (categories.IsFixed)
            {
                await writer.WriteAttributeStringAsync(App10Constants.Fixed, "yes");
            }

            await WriteAttributeExtensionsAsync(writer, categories, version);

            for (int i = 0; i < categories.Categories.Count; ++i)
            {
                await Atom10FeedFormatter.WriteCategoryAsync(writer, categories.Categories[i], version);
            }

            await WriteElementExtensionsAsync(writer, categories, version);
        }