title: Keras: Get True labels (y_test) from ImageDataGenerator or predict_generator
body: <p>I am using <code>ImageDataGenerator().flow_from_directory(...)</code> to generate batches of data from directories.</p>
  
  <p>After the model builds successfully I'd like to get a two column array of True and Predicted class labels. With <code>model.predict_generator(validation_generator, steps=NUM_STEPS)</code> I can get a numpy array of predicted classes. Is it possible to have the <code>predict_generator</code> output the corresponding True class labels?</p>
  
  <p>To add: validation_generator.classes does print the True labels but in the order that they are retrieved from the directory, it doesn't take into account the batching or sample expansion by augmentation.</p>