pub fn lens(&self) -> (usize, usize)
    where
        I: ExactSizeIterator,
    {
        match self.peeked {
            Some(Peeked::A(_)) => (1 + self.a.len(), self.b.len()),
            Some(Peeked::B(_)) => (self.a.len(), 1 + self.b.len()),
            _ => (self.a.len(), self.b.len()),
        }
    }
The arrays storing the actual data of the node. Only the first `le
benchmarks/haystacks/code/rust-library.rs