[{'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:unique_values_dict = {}\nfor col in train_df.columns:\nif col not in ["ID", "y", "X0", "X1", "X2", "X3", "X4", "X5", "X6", "X8"]:\nunique_value = str(np.sort(train_df[col].unique()).tolist())\ntlist = unique_values_dict.get(unique_value, [])\ntlist.append(col)\nunique_values_dict[unique_value] = tlist[:]\nunique_values_dict[\'[0]\']'}, {'role': 'assistant', 'content': 'data_preprocessing'}]