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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 oracle_approximating(self):
 """ Calculate the Oracle Approximating Shrinkage estimate :return: shrunk sample covariance matrix :rtype: np.ndarray """

        X = np.nan_to_num(self.X.values)
        shrunk_cov, self.delta = covariance.oas(X)
        return self.format_and_annualise(shrunk_cov)