ImageDataGenerator - trained with model.fit instead of model.fit_generator
The data augmentations are defined when you instantiate your data generators. An example is as such: 

train_datagen = ImageDataGenerator(
        rescale=1./255,
        shear_range=0.2,
        zoom_range=0.2,
        horizontal_flip=True)


Other augmentation techniques can also be used by setting the correct parameters. Refer to this link: https://keras.io/preprocessing/image/