TST: `replace_sublist` function is missing tests

[seberg]

The replace_sublist function is implemented and documented. However, it is still missing tests.

We should add new tests to check basic replacements. This may also allow us to improve the implementation in the future.

Working on the issue

Familiarize yourself with the replace_sublist functionality. Then add some basic tests. There are already two stubs to add them:

• test_replace_sublist_simple adding one or more examples.
• test_replace_sublist_overlap, because it may be relevant to see what happens if a sublist like [1, 1] can have overlapping lists.

You can start implement only one of these of course. Once implemented confirm that the tests works with pytest ..
Then make sure you committed all your changes to a branch and open a pull request!