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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 ack_deadline(self):
 """Return the current ack deadline based on historical time-to-ack. This method is "sticky". It will only perform the computations to check on the right ack deadline if the histogram has gained a significant amount of new information. Returns: int: The ack deadline. """

        target = min([self._last_histogram_size * 2, self._last_histogram_size + 100])
        if len(self.ack_histogram) > target:
            self._ack_deadline = self.ack_histogram.percentile(percent=99)
        return self._ack_deadline