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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 cvar_(self, col):
 """ Returns the coefficient of variance of a column in percentage """

        try:
            v = (np.std(self.df[col]) / np.mean(self.df[col])) * 100
            return v
        except Exception as e:
            self.err(e,
                     "Can not calculate coefficient of variance")