Hi Juma Khudonazarov,
Could you provide some more information?
Since you have posted it in the Python section I assume that you are doing this in the Python window of Pro (from the look of the error message).
Could you provide the code that you are using and/or an example of the xlsform?
Some context would also be handy, what are you trying to do, when does it occur, does it occur every time, that sort of thing.
We can not do much with the amount of information that you have provided.