The part where the function is called without an argument, like you need to do here. Just scroll a little bit and you'll find it.

Now you have to work out, how you can make the code work if no argument is passed to it.

You probably edited the sample tests, backup your code, click Reset, paste it and try again. Not a kata issue, the sample tests are fine in Python.

This is not a kata issue. You need to write a function that works with both 0 and 1 argument passed to it

That's a problem with your code, not a kata issue. Your code is doing a division by 0 for some input.

Note: Empty arrays should return 0.

Mark your post as having spoiler content next time and use markdown formatting, it's in the Codewars docs.