/// <summary>
        /// Handles the Structure top level elements
        ///     This includes Concept Scheme
        /// </summary>
        /// <param name="parent">
        ///     The parent <see cref="IMutableObjects"/>
        /// </param>
        /// <param name="localName">
        ///     The name of the current xml element
        /// </param>
        protected override ElementActions HandleTopLevel(IMutableObjects parent, object localName)
        {
            ElementActions actions = null;
            if (NameTableCache.IsElement(localName, ElementNameTable.ConceptScheme))
            {
                var cs = new ConceptSchemeMutableCore();
                ParseAttributes(cs, this.Attributes);
                parent.AddConceptScheme(cs);
                actions = this.AddNameableAction(cs, this.HandleChildElements);
            }

            return actions;
        }