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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def cancel(self):
 """Unschedule this call @raise AlreadyCancelled: Raised if this call has already been unscheduled. @raise AlreadyCalled: Raised if this call has already been made. """

        if self.cancelled:
            raise error.AlreadyCancelled
        elif self.called:
            raise error.AlreadyCalled
        else:
            self.canceller(self)
            self.cancelled = 1
            if self.debug:
                self._str = str(self)
            del self.func, self.args, self.kw