Unresolved attribute reference 'append' for class 'bool'

The problem arises after I use .update command. Someone pls explain why is it happening. The program works just fine. Its just that I wanna know why am I getting this warning.
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Hello,
I have reproduced and reported it as a bug https://youtrack.jetbrains.com/issue/PY-44911 , please vote for it in order to increase its priority and be updated on resolution.
Sorry for the inconvenience.