public async Task <ContentManageResult> RemoveMylistItem(MylistId mylistId, VideoId videoId)
        {
            var itemId = _loginUserMylistItemIdRepository.GetItemId(mylistId, videoId);

            if (mylistId.IsWatchAfterMylist)
            {
                return(await _niconicoSession.ToolkitContext.Mylist.LoginUser.RemoveWatchAfterItemsAsync(new[] { itemId }));
            }
            else
            {
                return(await _niconicoSession.ToolkitContext.Mylist.LoginUser.RemoveMylistItemsAsync(mylistId, new[] { itemId }));
            }
        }