/// <summary>
        /// Adds a model to the internal list which will check for duplicates.
        /// </summary>
        /// <param name="model"></param>
        public void Add(object model)
        {
            var key = _typeAccessor.GetModelKey(model);

            if (!_list.ContainsKey(key))
            {
                _list.Add(key, model);
            }
        }