How to use insertItemsAtIndexes:inParent:withAnimation (bug?)

[limura]

Thank you for a wonderful library.
I am working very well in the range that I am using and it is very helpful. Thank you very much.

There is one method which does not work well, so I am glad if you can tell us how to use it.
That is how to use "insertItemsAtIndexes: inParent: withAnimation" to add Cell.
This function seems to work normally in the usual way.
However, under certain conditions I did not do what I expected.

The situation can be reproduced by using the sample "TreeViewController.swift".

The situation which I think as a problem is as follows.

1. Run TreeViewController.swift with the simulator.
2. Open the Cell whose "Number of children" value is 1 or more. For example, open "Computers".
3. Check the "child cells" opened with "2.". Open the Cell whose "Number of children" value is 1 or more. For example, open "Computer 1".

The screen at this point is as follows.

  Computers
    Computer 1
      Notebook 1
      Notebook 2
    Computer 2
    Computer 3

4. In the state of "3." press the plus button on the right side of "Computers cell" to add a new cell.

In my expectation I thought that it would be as follows.

  Computers
    Computer 1
      Notebook 1
      Notebook 2
    Computer 2
    Computer 3
    Added value

However, it actually became as follows.

  Computers
    Computer 1
      Notebook 1
      Notebook 2
    Computer 2
    Computer 2
    Computer 3

If you added Cell without going through the "3." step (without opening grandchild Cell), "Added value cell" was added as expected.

I am misunderstanding how to use "insertItemsAtIndexes: inParent: withAnimation".
I hope you tell me.
Thank you for reading.