func NewSkiplist(arenaSize int64) *Skiplist {
	arena := newArena(arenaSize)
	head := newNode(arena, nil, y.ValueStruct{}, maxHeight)
	return &Skiplist{
		height: 1,
		head:   head,
		arena:  arena,
		ref:    1,
	}
}
func NewSkiplist(arenaSize int64) *Skiplist {
	arena := newArena(arenaSize)
	head := newNode(arena, nil, y.ValueStruct{}, maxHeight)
	return &Skiplist{
		height: 1,
		head:   head,
		arena:  arena,
		ref:    1,
	}
}
// NewSkiplist makes a new empty skiplist, with a given arena size