def METHOD_NAME(font_file, font_name=None):
    """Add a font description to our directory of externally loadable fonts.
    `font_file` is the path to the font, and optional `font_name` is the
    name to register it under.
    """
    global font_dir
    if font_name is None:
        # determine family name from filename of font
        dirname, filename = os.path.split(font_file)
        font_name, ext = os.path.splitext(filename)
    font_dir[font_name] = Bunch.Bunch(name=font_name, font_path=font_file)
    return font_name