def statevector(circuit):
    """ Get the qubit statevector.

    Args:
        circuit (renom_q.QuantumCircuit):
            A class of QuantumCircuit.

    Returns:
        (array):
            A array of the qubit statevector.

    Example:
        >>> import renom_q
        >>> q = renom_q.QuantumRegister(1)
        >>> c = renom_q.ClassicalRegister(1)
        >>> qc = renom_q.QuantumCircuit(q, c)
        >>> qc.x(q[0])
        >>> renom_q.statevector(qc)
        array([0.+0.j, 1.+0.j])
    """
    return circuit.Qr.qubit
