[{'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:from sklearn.linear_model import Ridge\nfrom sklearn.metrics import accuracy_score\n\nrlnrs = {}\nfor i, c in enumerate(np.unique(store_cluster)):\n    df_c = df_train[df_train.label == c]\n    if df_c.shape[0] == 0:\n        continue\n    X_c = df_c.drop(['Date', 'Sales', 'Customers'], axis=1).values\n    y_c = df_c.Sales.values\n    rlnr = Ridge()\n    rlnr.fit(X_c, y_c)\n    rlnrs.update({c: rlnr})\n    print(c, rlnr.score(X_c, y_c))"}, {'role': 'assistant', 'content': 'data_preprocessing'}]