[{'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:brandencoder = LabelEncoder().fit(phone.phone_brand)\nphone['brand'] = brandencoder.transform(phone['phone_brand'])\ngatrain['brand'] = phone['brand']\ngatest['brand'] = phone['brand']\nXtr_brand = csr_matrix((np.ones(gatrain.shape[0]), \n                       (gatrain.trainrow, gatrain.brand)))\nXte_brand = csr_matrix((np.ones(gatest.shape[0]), \n                       (gatest.testrow, gatest.brand)))\nprint('Brand features: train shape {}, test shape {}'.format(Xtr_brand.shape, Xte_brand.shape))"}, {'role': 'assistant', 'content': 'data_preprocessing'}]