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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 bures_angle(rho0: Density, rho1: Density) -> float: """Return the Bures angle between mixed quantum states Note: Bures angle cannot be calculated within the tensor backend. """

    return np.arccos(np.sqrt(fidelity(rho0, rho1)))