code: def ua_string(praw_info):
          
          if os.environ.get('SERVER_SOFTWARE') is not None:
              # Google App Engine information
              # https://developers.google.com/appengine/docs/python/
              info = os.environ.get('SERVER_SOFTWARE')
          else:
              # Standard platform information
              info = platform.platform(True).encode('ascii', 'ignore')
  
          return '{0} PRAW/{1} Python/{2} {3}'.format(
              praw_info, __version__, sys.version.split()[0], info)
docs: Return the user-agent string.
  
          The user-agent string contains PRAW version and platform version info.