[{'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 weighted_mae_custom(y_true, y_pred):\n    '''\n    Custom weighting function as specified in the evaluation section.\n    '''\n    weights = X_train_tf['IsHoliday']\n    sample_weights = pd.Series(weights.loc[y_true.index.values].values.reshape(-1)).dropna()\n    return (1.0 / np.sum(sample_weights)) * np.sum(sample_weights * np.abs(y_true - y_pred))\n\nweighted_mae = make_scorer(weighted_mae_custom)"}, {'role': 'assistant', 'content': 'helper_functions'}]