[{'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.ensemble import ExtraTreesClassifier\nfrom sklearn.metrics import classification_report\nx_data, x_test_data, y_data, y_test_data = train_test_split(X_train,y_train,test_size= 0.3, random_state=0)\netc_para = [{'n_estimators': [20, 30, 100], 'max_depth':[5, 10, 15], 'max_features': [0.1, 0.2, 0.3]}]\n#default number of features is sqrt(n)\n#default number of min_samples_leaf is 1"}, {'role': 'assistant', 'content': 'data_preprocessing'}]