一运行程序报错
请问为什么运行下载代码的程序时，会出现这样的情况呢：
Traceback (most recent call last):
File "C:\Users\yuanqi\Desktop\dangdang.py", line 102, in <module>
main()
File "C:\Users\yuanqi\Desktop\dangdang.py", line 97, in main
result = d.parse_item(items=items)
File "C:\Users\yuanqi\Desktop\dangdang.py", line 50, in parse_item
for item in items:
TypeError: 'NoneType' object is not iterable
