def add_density_option_group(parser):
    """Adds the options needed to configure contours and density colour map.

    Parameters
    ----------
    parser : object
        ArgumentParser instance.
    """
    density_group = parser.add_argument_group(
        'Options for configuring the contours and density color map')
    density_group.add_argument('--density-cmap', type=str, default=
        'viridis', help=
        'Specify the colormap to use for the density. Default is viridis.')
    density_group.add_argument('--contour-color', type=str, default=None,
        help=
        'Specify the color to use for the contour lines. Default is white for density plots and black for scatter plots.'
        )
    density_group.add_argument('--use-kombine-kde', default=False, action=
        'store_true', help=
        "Use kombine's KDE for determining contours. Default is to use scipy's gaussian_kde."
        )
    return density_group
