[{'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:b"# Fill null values\\ntrain_df[\'State\'].fillna(\'No State\', inplace=True)\\ntest_df[\'State\'].fillna(\'No State\', inplace=True)\\n\\n# Number of missing values in each column of training data\\nmissing_train_count_col = (train_df.isnull().sum())\\nprint(missing_train_count_col[missing_train_count_col>0])\\n\\n# Number of missing values in each column of training data\\nmissing_test_count_col = (test_df.isnull().sum())\\nprint(missing_test_count_col[missing_test_count_col>0])\\nprint(\'\\\\n\')\\n\\n# Double check no remaining missing values\\ntrain_df.info()\\nprint(\'\\\\n\')\\ntest_df.info()"'}, {'role': 'assistant', 'content': 'data_preprocessing'}]