code: def url_is_alive(url):
      
      request = urllib.request.Request(url)
      request.get_method = lambda: 'HEAD'
  
      try:
          urllib.request.urlopen(request)
          return True
      except urllib.request.HTTPError:
          return False
docs: Checks that a given URL is reachable.
      :param url: A URL
      :rtype: bool