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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 std(self, values, axis=0, weights=None, dtype=None):
 """standard deviation over each group Parameters values to take standard deviation of per group axis : int, optional alternative reduction axis for values Returns ------- unique: ndarray, [groups] unique keys value array, reduced over groups """

        unique, var = self.var(values, axis, weights, dtype)
        return unique, np.sqrt(var)