The `find_item` example uses List for an argument. To my thinking, this indicates that the function is intended to mutate the argument. I don't think that was t

The `find_item` example uses List for an argument. To my thinking, this indicates that the function is intended to mutate the argument. I don't think that was the author's intention, though, so I would prefer to use Sequence in this situation (or possibly Iterable, if we only need to traverse the sequence once in order).