[{'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 loss_func(truth, prediction):\n    truth = np.expm1(truth)\n    prediction = np.expm1(prediction)\n    log1 = np.array([np.log(x + 1) for x in truth])\n    log2 = np.array([np.log(x + 1) for x in prediction])\n    return np.sqrt(np.mean((log1 - log2)**2))'}, {'role': 'assistant', 'content': 'helper_functions'}]