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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 max_rain(self):
 """Returns a tuple containing the max value in the rain series preceeded by its timestamp :returns: a tuple :raises: ValueError when the measurement series is empty """

        return max(self._purge_none_samples(self.rain_series()),
                   key=lambda item:item[1])