[DF][NFC] Use [] instead of `at`: the element must be there
[DF][NFC] Use [] instead of `at`: the element must be there

karies/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,olifre/root,karies/root,olifre/root,karies/root,karies/root,olifre/root,olifre/root,karies/root,karies/root,root-mirror/root,root-mirror/root,olifre/root