[{'role': 'system', 'content': "You are an expert in machine learning and your task is to classify code snippets into one of the following categories: ['helper_functions', 'load_data', 'data_exploration', 'data_preprocessing', 'evaluation', 'modelling', 'prediction', 'result_visualization', 'save_results', 'comment_only']."}, {'role': 'user', 'content': 'Identify the single most appropriate category to which the provided code belongs. Provide your response as a single category label without any additional information, commentary, or personal opinions.\\nPython Code:import tensorflow as tf\nimport keras\nfrom keras.preprocessing.image import ImageDataGenerator\n\ntrain_gen = ImageDataGenerator(\n    rotation_range=20,\n    #width_shift_range=0.2,\n    #height_shift_range=0.2,\n    shear_range=0.2,\n    zoom_range=0.2,\n    #channel_shift_range=0.2,\n    horizontal_flip=True,\n    #vertical_flip=True,\n    #rescale=1./255,#!!!!NO!\n    preprocessing_function=lambda x:(x-x.mean())/x.std()\n)\ntest_gen = ImageDataGenerator(\n    #rescale=1./255,\n    preprocessing_function=lambda x:(x-x.mean())/x.std()\n)'}, {'role': 'assistant', 'content': 'helper_functions'}]