fn new() -> Box<Self> {
        unsafe {
            let mut leaf = Box::new_uninit();
            LeafNode::init(leaf.as_mut_ptr());
            leaf.assume_init()
        }
    }
A reference to a node.

This type has a number of parameters that controls how it acts:
- `BorrowType`: A dummy type that describes the kind of borrow and carries a lifetime.
- When this is `Immut<'a>`, the `NodeRef` acts roughly like `&'a Node`.
- When this is `ValMut<'a>`, the `NodeRef` acts roughly like `&'a Node`
with respect to keys and tree structure, but also
benchmarks/haystacks/code/rust-library.rs