[{'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:alpha = pm.Normal("alpha", 0, 1.0/50**2)\nbeta = pm.Exponential("beta", 1.0/100)\n@pm.stochastic(name="obs", dtype=np.float64, observed=True)\ndef obs(value=data, alpha=alpha, beta=beta):\nreturn np.sum(np.log(beta) - np.log(np.pi) - np.log(beta**2 + (alpha-value)**2))\nmodel = pm.Model([alpha, beta, obs])\nutils.display_graph(model)'}, {'role': 'assistant', 'content': 'modelling'}]