[{'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:# df_gender_age_train.device_id[]\nin_train_events = df_events[df_events.device_id.isin(set(df_gender_age_train.device_id) & set(df_events.device_id))]\nin_train_app_events = df_app_events[df_app_events.event_id.isin(in_train_events.event_id)]\nin_train_app_events.event_id.nunique(), in_train_app_events.event_id.size, len(in_train_events)'}, {'role': 'assistant', 'content': 'data_preprocessing'}]