def pop(self):
    '\n        :rtype: void\n        '
    top = self.stack1[(- 1)]
    self.stack1.pop()
    if (top == self.stack2[(- 1)]):
        self.stack2.pop()
:rtype: void
def pop(self):
    '\n        \n        '
    top = self.stack1[(- 1)]
    self.stack1.pop()
    if (top == self.stack2[(- 1)]):
        self.stack2.pop()