def category_styledict(colordict, highlight_grp):
    """Generate a dictionary mapping categories to styles.

    The only styling implemented at present is converting the highlighted group to a dashed line.

    Args:
        colordict (dict) A mapping of categories to colors
        highlight_grp (string) The name of a group/category that should be highlighted

    Returns: (dict) A mapping of categories to matplotlib styles
    """
    return dict(
        (key, "--" if key == highlight_grp else "-") for key in colordict.keys()
    )