Chess AI undoing a move

[MichaelMortimer]

I have created a chess program but am stuck on one specific part. If I am playing against an AI but want to undo a move, I am unable to do so. Instead of undoing my previous move, the AI just picks another move. Here is the code:

                if e.key == p.K_z: 
                    GS.UndoMove() #Undo the last move
                    MoveMade = True
                    Animate = False #Don't animate the pieces returning to their previous positions
                    GameOver = False #No player has won yet
                    if AIThinking:
                        MoveFinderProcess.terminate() #Stops the AI about thinking about potential moves as we don't know what move will be played next
                        AIThinking = False
                    MoveUndone = True

I understand that this question isn't the clearest but any help would be much appreciated

[dev7060]

What kind of interpretation one could have from these lines to even remotely approach the solution?

[markopalme]

Thanks for this interesting information!