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

mm = tafunc.ref(HAhigh, 1) - tafunc.ref(HAlow, 1)
                    nn = tafunc.ma(mm, 6)