/// let elements = vec![Enum::A(1), Enum::A(2), Enum::B(3), Enum::A(4)];
///
/// assert_eq!(find_extract!(elements.iter(), Enum::B(x), x), Some(3u16));
/// let elements = vec![Enum::A(1), Enum::A(2), Enum::B(3), Enum::A(4)];
///
/// assert_eq!(find_extract!(elements.iter(), Enum::B(x), x), Some(3u16));