don't mutate the list

same problem

This is the problem I'm having. Pass first test and fail 2 and 3. I think its the null, undefined aspect. I have code to rule out values which are NOT true but this still not working.

Same here.

Update: if this happens to you, copy your code to the clipboard, reset the kata and paste it right back down. Worked.

Hey, How did you pass this kata? I pass the first one and then when I click attemp, I fail 2 and 3

Because you forgot some parentheses and integers are not iterables.

Hint: Don't forget to check for bad values like null/undefined

read the hint in the description

Still you don't show your code.

We don't know.

Maybe this will be helpful? https://docs.codewars.com/training/troubleshooting