[{'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:#Using pd.to_datetime for adding new features\ndf_train['Date'] = pd.to_datetime(df_train['Date'])\ndf_train.insert(1,'Week',df_train['Date'].dt.week)\ndf_train.insert(2,'Day',df_train['Date'].dt.day)\ndf_train.insert(3,'DayofWeek',df_train['Date'].dt.dayofweek)\ndf_train.insert(4,'DayofYear',df_train['Date'].dt.dayofyear)\n\ndf_test['Date'] = pd.to_datetime(df_test['Date'])\ndf_test.insert(1,'Week',df_test['Date'].dt.week)\ndf_test.insert(2,'Day',df_test['Date'].dt.day)\ndf_test.insert(3,'DayofWeek',df_test['Date'].dt.dayofweek)\ndf_test.insert(4,'DayofYear',df_test['Date'].dt.dayofyear)"}, {'role': 'assistant', 'content': 'data_preprocessing'}]