[{'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:# Thank to notebooks we can definve evaluation metric\n\ndef ToWeight(y):\n    w = np.zeros(y.shape, dtype=float)\n    ind = y != 0\n    w[ind] = 1./(y[ind]**2)\n    return w\n\n\ndef rmspe(yhat, y):\n    w = ToWeight(y)\n    rmspe = np.sqrt(np.mean( w * (y - yhat)**2 ))\n    return rmspe'}, {'role': 'assistant', 'content': 'helper_functions'}]