pub unsafe fn new_edge(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
        debug_assert!(idx <= node.len());

        Handle { node, idx, _marker: PhantomData }
    }
Inserts a new key-value pair between the key-value pairs to the right and left of
this edge. This method splits the node if there isn't enough room.

The returned
benchmarks/haystacks/code/rust-library.rs