[{'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:features = df_train_store.drop(['Customers', 'Sales', 'SalesperCustomer'], axis = 1) \n#a rule of thumb is to transform my target value to log if i see the values are very dispersed which is the case\n#and then of course revert them with np.exp to their real values\ntargets=np.log(df_train_store.Sales)\n"}, {'role': 'assistant', 'content': 'data_preprocessing'}]