We want to add a button to the tally counter in section 9.2 that


1.     We  want to add a button to the tally counter in Section 9.2 that allows an  operator to undo accidental button click. Provide a method

def undo(self)

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 that simulates such a button. As an added precaution, make sure an undo doesn’t cause the counter to be less than zero.

a)    Your code with comments

b)    A screenshot of the execution

Test Case:


2 clicks

Print Value

1 click

Print Value

2 undos

Print Value

2 undos

Print Value

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