/// <summary>
 /// Saves a model in a zip file.
 /// </summary>
 public static void SaveModel(TlcEnvironment env, IDataTransform tr, string outModelFilePath)
 {
     using (var ch = env.Start("SaveModel"))
         using (var fs = File.Create(outModelFilePath))
         {
             var trainingExamples = env.CreateExamples(tr, null);
             TrainUtils.SaveModel(env, ch, fs, null, trainingExamples);
         }
 }