[{'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.model_selection import StratifiedShuffleSplit\n\nsplit = StratifiedShuffleSplit(n_splits=1, test_size=0.2, random_state=42)\n\nfor train_index, test_index in split.split(X, y):\n    strat_train_set = data.iloc[train_index]\n    strat_test_set = data.iloc[test_index]\n\nX_train = strat_train_set.drop('ACTION', axis=1)\ny_train = strat_train_set['ACTION'].copy()\nX_test = strat_test_set.drop('ACTION', axis=1)\ny_test = strat_test_set['ACTION'].copy()\nX_train.shape, X_test.shape"}, {'role': 'assistant', 'content': 'data_preprocessing'}]