[{'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:predict = []\ncas = LinearRegression().fit(x2_train, y2_train)\npre_cas = cas.predict(x2_test)\n\ncas_poly = LinearRegression().fit(poly_x2_train, y2_train)\npre_cas_poly = cas_poly.predict(poly_x2_test)\n\nrf_cas = GridSearchCV(rf, parameters, cv=5, verbose=2,scoring = scorer,n_jobs = -1)\nrf_cas.fit(x2_train, y2_train)\npre_rf_cas = rf_cas.predict(x2_test)\n\npredict.append(pre_cas)\npredict.append(pre_cas_poly)\npredict.append(pre_rf_cas)'}, {'role': 'assistant', 'content': 'modelling'}]