And generally, if you are passed an owned parameter or variable x, you can usually declare it as `mut x` right from the very start. So in the examples given, rather than the identity function or anything fancy like that, you can just write:

    fn consume_the_list(mut self) {
        // self is mutable here
    }

This is generally true for any other owned parameter, with the distinction that the `mut` applies to the parameter pattern and not the type. (i.e. `mut val: String`, not `val: mut String`).