[{'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:def clean_deaths(row):\nnum_deaths = 0\ncolumns = ['Death1', 'Death2', 'Death3', 'Death4', 'Death5']\nfor c in columns:\ndeath = row[c]\nif pd.isnull(death) or death == 'NO':\ncontinue\nelif death == 'YES':\nnum_deaths += 1\nreturn num_deaths\ntrue_avengers1=true_avengers.copy()\ntrue_avengers1['Deaths'] = true_avengers1.apply(clean_deaths, axis=1)\ntrue_avengers = true_avengers1\ntrue_avengers"}, {'role': 'assistant', 'content': 'data_preprocessing'}]