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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 mixed_density(qubits: Union[int, Qubits]) -> Density: """Returns the completely mixed density matrix"""

    N, qubits = qubits_count_tuple(qubits)
    matrix = np.eye(2**N) / 2**N
    return Density(matrix, qubits)