code: func (n *node) markBeingDeleted() {
  	n.beingDeletedLock.Lock()
  	defer n.beingDeletedLock.Unlock()
  	n.beingDeleted = true
  }
docs: // An object is on a one way trip to its final deletion if it starts being
  // deleted, so we only provide a function to set beingDeleted to true.