code: def add_font(font_file, font_name=None):
      
      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
docs: 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.