[{'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:def prepare(df):\n    # transform the date into something human-meaningful\n    df['Year'] = pd.DatetimeIndex(df.Date).year\n    df['Month'] = pd.DatetimeIndex(df.Date).month\n    df['Day'] = pd.DatetimeIndex(df.Date).day\n    # encode StateHolidays into numbers\n    # Since there are only 'a' state holidays in test set, I can probably map a, b, c into 1\n    df[df.StateHoliday != '0'] = 1\n    df.StateHoliday = pd.to_numeric(df.StateHoliday)\n    return df"}, {'role': 'assistant', 'content': "['data_preprocessing']"}]