def METHOD_NAME(roi, bundle_name="ROI"):
    """
    After being non-linearly transformed, ROIs tend to have holes in them.
    We perform a couple of computational geometry operations on the ROI to
    fix that up.
    Parameters
    ----------
    roi : 3D binary array
        The ROI after it has been transformed.
    bundle_name : str, optional
        Name of bundle, which may be useful for error messages.
        Default: None
    Returns
    -------
    ROI after dilation and hole-filling
    """
    hole_filled = ndim.binary_fill_holes(roi > 0)
    if not np.any(hole_filled):
        raise ValueError((
            f"{bundle_name} found to be empty after "
            "applying the mapping."))
    return hole_filled