Fixed linked list bug (#2481)

* * fixed __getitem__() function
* add test

* * updated doctests
* updated __setitem__() func

* fixup! Format Python code with psf/black push

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

Du Yuanchao committed 5y ago

b81fcef66bc4dc6fae2594998404d0cac8504b1c

Parent: 18f1dcd

Committed by GitHub <noreply@github.com> on 9/25/2020, 4:08:57 PM