[{'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:train_df_dscb = train_df.describe(percentiles=[.96])\nfor col in [x for x in train_df_dscb.columns.values if x not in ['id'] and x[0:9] != 'sub_area_']:\nprint(col, end='//')\ntrain_df[col] = train_df.ix[:, col].apply(lambda x: (x-train_df_dscb[col]['min'])/(train_df_dscb[col]['96%']-train_df_dscb[col]['min']))"}, {'role': 'assistant', 'content': 'data_preprocessing'}]