code: public void lockEdgeInternal(String childName, LockMode mode) {
      Preconditions.checkState(endsInInode());
  
      Inode lastInode = get(numLockedInodes() - 1);
      Edge edge = new Edge(lastInode.getId(), childName);
      mEntries.add(new EdgeEntry(mInodeLockManager.lockEdge(edge, mode), edge));
    }
docs: Locks the next edge without checking or updating the mode.
  
  @param childName the child to lock
  @param mode the mode to lock in