[{'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:store['Promo2SinceYear']=store['Promo2SinceYear'].fillna(store['Promo2SinceYear'].mode().iloc[0])\n#technically its wrong to say promos missed for 2 years but for current scenrio we can fill it with mode\n\nstore['PromoInterval']=store['PromoInterval'].fillna(store['PromoInterval'].mode().iloc[0])\n\n#its obvious that there is no competitor\nstore['CompetitionDistance']=store['CompetitionDistance'].fillna(0)\nstore['CompetitionOpenSinceMonth']=store['CompetitionOpenSinceMonth'].fillna(store['CompetitionOpenSinceMonth'].mode().iloc[0])\nstore['CompetitionOpenSinceYear']=store['CompetitionOpenSinceYear'].fillna(store['CompetitionOpenSinceYear'].mode().iloc[0])"}, {'role': 'assistant', 'content': 'data_preprocessing'}]