code: def infer_theme():
      
      themes = [os.path.basename(theme).replace('.less', '')
                    for theme in glob('{0}/*.less'.format(styles_dir))]
      if os.path.exists(theme_name_file):
          with open(theme_name_file) as f:
              theme = f.readlines()[0]
          if theme not in themes:
              theme = 'default'
      else:
          theme = 'default'
  
      return theme
docs: checks jupyter_config_dir() for text file containing theme name
      (updated whenever user installs a new theme)