code: def user_agent(style=None) -> _UserAgent:
      
      global useragent
      if (not useragent) and style:
          useragent = UserAgent()
  
      return useragent[style] if style else DEFAULT_USER_AGENT
docs: Returns an apparently legit user-agent, if not requested one of a specific
      style. Defaults to a Chrome-style User-Agent.