Function polygon2::union

pub fn union<T>(subject: &[[T; 2]], clip: &[[T; 2]]) -> Vec<Vec<[T; 2]>> where
    T: Clone + Signed + PartialEq + PartialOrd,
    &'a T: Div<&'b T, Output = T> + Sub<&'b T, Output = T> + Add<&'b T, Output = T> + Mul<&'b T, Output = T>,