/// <summary>
        /// save serialized file
        /// </summary>
        /// <param name="filePath">where file will be saved</param>
        /// <param name="extension">json or xml</param>
        /// <param name="fileName">name of output file</param>
        /// <param name="loadedGroups">data for serialization</param>
        private static void SaveFile(string filePath, string extension, string fileName, OutputModel loadedGroups)
        {
            string fullpath;

            switch (extension)
            {
            case "xml":
                fullpath = Path.Combine(filePath, fileName + ".xml");
                FileSaver.SerialToXmlFile(fullpath, loadedGroups);
                Console.WriteLine($"File saved to {fullpath}");
                break;

            case "json":
                fullpath = Path.Combine(filePath, fileName + ".json");
                FileSaver.SerialToJsonFile(fullpath, loadedGroups);
                Console.WriteLine($"File saved to {fullpath}");
                break;

            default:
                Console.WriteLine($"Not valid type of extension: '{extension}'");
                break;
            }
        }