[{'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:teamSalaryPerYear = list()\nfor year in salarydf.Year.unique():\nyear_df = salarydf.loc[salarydf.Year == year]\nfor team in year_df.Team.unique():\nteam_df = year_df.loc[year_df.Team == team]\nsalary_total = team_df.Salary.sum(axis=0)\nteamSalaryPerYear.append((year,team,salary_total))'}, {'role': 'assistant', 'content': 'data_preprocessing'}]