func (nt *NodeTable) MemoryInUse() int64 {
	return int64(approxItemSize * (nt.fastHTCount + nt.slowHTCount))
}
func (nt *NodeTable) MemoryInUse() int64 {
	return int64(approxItemSize * (nt.fastHTCount + nt.slowHTCount))
}
// MemoryInUse returns memory used by nodetable instance