The first one (index 0) is `None` because there is a `None` for index 0 in `second_try`. The second is `None` because there is a `None` in `first_try`. The next is `Some("success!")` because there is no `None` for `first_try`, `second try`, or `third_try`.
`.any()` and `.all()` are very easy to use in iterators. They return a `bool` depending on your input. In this example we make a very large vec (about 20,000 items) with all the characters from `'a'` to `'働'`. Then we make a function to check if a character is inside it.
Next we make a smaller vec and ask it whether it is all alphabetic (with `.is_alphabetic()`). Then we ask it if all the characters are less than the Korean character `'행'`.
Also note that you put a reference in, because `.iter()` gives a reference and you need a `&` to compare with another `&`.