ut
    losing the block structure.

    Parameters
    ----------
    a : ndarray
        The permutation array ipiv returned by LAPACK
    lower : bool, optional
        The switch to select whether upper or lower triangle is chosen in
        the LAPACK call.

    Returns
    -------
    swap_ : ndarray
        The array that defines the row/column swap operations. For example,
        if row two is swapped with row four, the result is [0, 3, 2, 3].
    pivots : ndarray
        The array that defines the block diagonal structure as given above.

    r