code: def get_urls_from_seed(url):
    
  
    if not url or type(url) != str or not naarad.utils.is_valid_url(url):
      logger.error("get_urls_from_seed() does not have valid seeding url.")
      return
  
    # Extract the host info of "http://host:port/" in case of href urls are elative urls (e.g., /path/gc.log)
    # Then join (host info and relative urls) to form the complete urls
    base_index = url.find('/', len("https://"))   # get the first "/" after http://" or "https://"; handling both cases.
    base_url = url[:base_index]      # base_url = "http://host:port" or https://host:port" or http://host" (where no port is given)
  
    # Extract the "href" denoted urls
    urls = []
    try:
      response = urllib2.urlopen(url)
      hp = HTMLLinkExtractor()
      hp.feed(response.read())
      urls = hp.links
      hp.close()
    except urllib2.HTTPError:
      logger.error("Got HTTPError when opening the url of %s" % url)
      return urls
  
    # Check whether the url is relative or complete
    for i in range(len(urls)):
      if not urls[i].startswith("http://") and not urls[i].startswith("https://"):    # a relative url ?
        urls[i] = base_url + urls[i]
  
    return urls
docs: get a list of urls from a seeding url, return a list of urls
  
    :param str url: a full/absolute url, e.g. http://www.cnn.com/logs/
    :return: a list of full/absolute urls.