[{'role': 'system', 'content': "You are an expert in machine learning and your task is to classify the code snippets into categories from the provided list of categories. List of categories: ['helper_functions', 'load_data', 'data_exploration', 'data_preprocessing', 'evaluation', 'modelling', 'prediction', 'result_visualization', 'save_results', 'comment_only']"}, {'role': 'user', 'content': "Identify to which category the provided code belongs and assign the code snippet to at least 1 but up to 5 categories based on the probabilities, ignore if the probability of the category is negligible. Strictly provide your response as a list. Avoid providing any additional information, commentary, or personal opinions.\\nPython Code:df_traintest3 = []\nfor place in places[:]:\n    df_tmp = df_traintest2[df_traintest2['place_id']==place].reset_index(drop=True)\n    df_tmp = do_aggregations(df_tmp)\n    df_traintest3.append(df_tmp)\ndf_traintest3 = pd.concat(df_traintest3).reset_index(drop=True)\ndf_traintest3[df_traintest3['place_id']=='China/Hubei'].head()"}, {'role': 'assistant', 'content': "['data_preprocessing']"}]