code: def normalize_urls(urls):
      
      _urls = []
      if isinstance(urls, list):
          if urls:
              if isinstance(urls[0], list):
                  # multiple connections (list of the lists)
                  _urls = urls
              elif isinstance(urls[0], str):
                  # single connections (make it list of the lists)
                  _urls = [urls]
          else:
              raise RuntimeError("No target host url provided.")
      elif isinstance(urls, str):
          _urls = [[urls]]
      return _urls
docs: Overload urls and make list of lists of urls.