[{'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:X_test = testdf.copy()\n\nX_test['people_pb'] = X_test.population/X_test.total_bedrooms\nX_test['people_ph'] = X_test.population/X_test.households\nX_test['income_pr'] = X_test.median_income/X_test.total_rooms\n\nX_test = X_test.filter(['median_age','total_rooms', 'total_bedrooms', 'population', 'households', 'median_income', 'city_price', 'people_pb','people_ph', 'income_pr'], axis = 1)\nX_test.describe()"}, {'role': 'assistant', 'content': 'data_preprocessing'}]