[{'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 simulate_GARCH(T, a0, a1, b1, sigma1):\nX = np.ndarray(T)\nsigma = np.ndarray(T)\nsigma[0] = sigma1\nfor t in range(1, T):\nX[t - 1] = sigma[t - 1] * np.random.normal(0, 1)\nsigma[t] = math.sqrt(a0 + b1 * sigma[t - 1]**2 + a1 * X[t - 1]**2)\nX[T - 1] = sigma[T - 1] * np.random.normal(0, 1)\nreturn X, sigma'}, {'role': 'assistant', 'content': 'modelling'}]