• A problem in solution checking?

Question related to mission Remove All Before

 

I clearly made the code work, but the Check gives me this error despite the "offending" import being part of the base code:

"ImportError: The module `builtins` is not allowed on checkio. Please see https://checkio.org/forum/post/3268/5-modules/ <module>, 1"

So am I supposed to somehow replace the "list" functionality as well?