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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 as_2d(self):
 """ get a 2D representation of x. If not self.isdiagonal, simply return reference to self.x, otherwise, constructs and returns a 2D, diagonal ndarray Returns ------- numpy.ndarray : numpy.ndarray """

        if not self.isdiagonal:
            return self.x
        return np.diag(self.x.flatten())