[{'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 null_percentage(column):\n    df_name = column.name\n    nans = np.count_nonzero(column.isnull().values)\n    total = column.size\n    frac = nans / total\n    perc = int(frac * 100)\n    print('%d%% of values or %d missing from %s column.' % (perc, nans, df_name))\n\ndef check_null(df, columns):\n    for col in columns:\n        null_percentage(df[col])\n        \ncheck_null(df, df.columns)"}, {'role': 'assistant', 'content': "['data_exploration']"}]