code: func (n *node) size() int {
  	sz, elsz := pageHeaderSize, n.pageElementSize()
  	for i := 0; i < len(n.inodes); i++ {
  		item := &n.inodes[i]
  		sz += elsz + len(item.key) + len(item.value)
  	}
  	return sz
  }
docs: // size returns the size of the node after serialization.