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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 average(self, rho):
 r"""Return the average density matrix of an inhomogeneous ensemble."""

        def marginal(f, rho):
            remaining = len(f.shape)
            if remaining == 0:
                return rho
            rho = sum([f[i]*rho[i] for i in range(rho.shape[0])])
            f = np.sum(f, 0)
            return marginal(f, rho)

        return marginal(self.distribution, rho)