请问 UnboundLocalError: local variable 'nn' referenced before assignment是个什么问题?File "C:/TianQin/strategies/singlema_tdtphama.py", line 1833, in tdtphama_2 print("nn.iloc[-1+i ]:",nn.iloc[-1+i]) UnboundLocalError: local variable 'nn' referenced before assignment 我是用异步函数写的,单独运行一个品种不报错,运行多个就报错了 api = TqApi(backtest=TqBacktest(start_dt=date(2020, 3, 9), end_dt=date(2020, 3, 9))) # 获得 m1901 5分钟K线的引用 klines = api.get_kline_serial("DCE.m2005", 30,...