Create the following structures. Each has one element:
- `One`:
- `One`: `first_layer` as type `Option<Two>`.
- which contains one element called `first_layer` which should be an `Option` of the structure `Two`.
- `Two`: `second_layer` as type `Option<Three>`
- `Two`:
- `Three`: `third_layer` as type `Option<Four>`
- which contains one element called `second_layer` which should be an `Option` of the structure `Three`.
- `Four`: `fourth_layer` as type `Option<u16>`.
- `Three`:
- which contains one element called `third_layer` which should be an `Option` of the structure `Four`.
- `Four`:
- which contains one element called `fourth_layer` which is an `Option<u16>`.
Beside the structure you must create a **function** named `get_fourth_layer` which is associated to the `One` structure (a method).
Beside the structures, you must create a **function** named `get_fourth_layer`, and associate it to the `One` structure. This **function** should return the `Option` value in the `Four` structure.
This **function** should return the `Option` value in the `Four` structure.
### Notions
- [Unpacking options with ?](https://doc.rust-lang.org/stable/rust-by-example/error/option_unwrap/question_mark.html)
### Expected Function and structures
### Expected Function and structures
@ -74,3 +65,7 @@ $ cargo run
1000
1000
$
$
```
```
### Notions
- [Unpacking options with ?](https://doc.rust-lang.org/stable/rust-by-example/error/option_unwrap/question_mark.html)