学习陈云老师的《深度学习框架PyTorch:入门与实践 》猫狗二分类实战时遇到的问题。
运行环境：
问题描述：

(pytorch) D:\SoftWares-Academic\python_workspace\pytorch-best-practice>python main.py help

    usage : python file.py <function> [--args=value]
    <function> := train | test | help
    example:
            python main.py train --env='env0701' --lr=0.01
            python main.py test --dataset='path/to/dataset/root/'
            python main.py help
    avaiable args:
Traceback (most recent call last):
  File "main.py", line 171, in <module>
    import fire
  File "D:\SoftWares-Academic\Anaconda3\envs\pytorch\lib\site-packages\fire\core.py", line 138, in Fire
    component_trace = _Fire(component, args, parsed_flag_args, context, name)
  File "D:\SoftWares-Academic\Anaconda3\envs\pytorch\lib\site-packages\fire\core.py", line 468, in _Fire
    target=component.__name__)
  File "D:\SoftWares-Academic\Anaconda3\envs\pytorch\lib\site-packages\fire\core.py", line 672, in _CallAndUpdateTrace
    component = fn(*varargs, **kwargs)
  File "main.py", line 166, in help
    from inspect import getsource
NameError: name 'opt' is not defined

很迷的错误，跟书附带的代码一样的。在main.py函数头部已经添加了from config import opt，但是还报错NameError: name ‘opt’ is not defined。
最后，在调用的方法help里直接添加from config import opt，没有错误了，但不知道原理。