Add IndexWrapper for yolo_io

[shirok1]

[tzutalin]

Could you provide more description about this PR? what is the issue?

[shirok1]

labelImg occasionally remove classes in class.txt (the whole line deleted), then labelImg will crash because failed to find corresponding class name from class.txt .

[tzutalin]

I see. I don't think the below solution is to fix the root cause. Instead of catching the index error, do you dive deeper or have other alternatives?

         try:
            result = self.content[index]
        except IndexError:
            return str(index)

Thanks

[shirok1]

Well, I think it's inefficient to use try-catch in an __gettitem__ method, which will be called in a loop. Anyway, I believe it is more important to fix the bug of deleting classes...

[tzutalin]

Hi @shirok1 , Thanks. Do you have an idea why/when labelImg occasionally remove classes in class.txt (the whole line deleted)? or how to reproduce it? Does it delete from memory or file? The solution probably work, but I would like to know more if there is another alternative to fix in the root ?