code: def get_lib_filename(category, name):
      
      base_dir = os.path.dirname(os.path.abspath(__file__))
      if category == 'js':
          filename = os.path.join('js', '{0}.js'.format(name))
      elif category == 'css':
          filename = os.path.join('css', '{0}.css'.format(name))
      elif category == 'html':
          filename = os.path.join('html', '{0}.html'.format(name))
      else:
          raise ValueError("Unknown category")
      return os.path.join(base_dir, 'lib', filename)
docs: Get a filename of a built-in library file.