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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):
 """Cancel the future if possible. Returns True if the future was cancelled, False otherwise. A future cannot be cancelled if it is running or has already completed. """

        with self._condition:
            if self._state in [RUNNING, FINISHED]:
                return False

            if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                return True

            self._state = CANCELLED
            self._condition.notify_all()

        self._invoke_callbacks()
        return True