# Re: \[PATCH\] selftests: tc-testing: fix list\_categories() crash on list type

- From: Jakub Kicinski \<kuba@kernel.org\>
- Date: 2026-03-04 02:17:03 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/03/3439023
- Thread: https://ratatoskr.run/netdev/2026/02/3432255/t.md

```text
On Sat, 28 Feb 2026 13:17:35 +0530 mr.navi8680@gmail.com wrote:
> list_categories() builds a set directly from the 'category'
> field of each test case. Since 'category' is a list,
> set(map(...)) attempts to insert lists into a set, which
> raises:
> 
>   TypeError: unhashable type: 'list'
> 
> Flatten category lists and collect unique category names
> using set.update() instead.

How did you find this issue?

I can't figure out what's calling this function in the first place.
-- 
pw-bot: cr
```