Similar features to #1 but with a pointer to the previous node. The `previous` pointer of the first node should be an `Option` as `None`, as well as the pointer to the `next` pointer for the last node.
Similar features to #1 but with a pointer to the previous node.
The
previouspointer of the first node should be anOptionasNone, as well as the pointer to thenextpointer for the last node.