[{'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 scipy as sp\nlena = sp.misc.ascent()\nlena = -lena + 255\nlena_patches = []\nfor i in range(4):\nfor j in range(4):\nlena_patches.append(lena[i::4, j::4])\nlena = lena_patches[0]\nplt.figure(figsize=(5, 5))\nplt.imshow(lena, cmap=plt.cm.gray)'}, {'role': 'assistant', 'content': 'data_preprocessing'}]