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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 pct_negative(self, threshold=0.0):
 """Pct. of periods in which `self` is less than `threshold.` Parameters threshold : {float, TSeries, pd.Series}, default 0. Returns ------- float """


        return np.count_nonzero(self[self < threshold]) / self.count()