docs: def do_health_checks(self, list_of_ips):
          """
          Perform a health check on a list of IP addresses.
  
          Each check (we use a TCP connection attempt) is run in its own thread.
  
          Gather up the results and return the list of those addresses that
          failed the test and the list of questionable IPs.
  
          TODO: Currently, this starts a thread for every single address we want
          to check. That's probably not a good idea if we have thousands of
          addresses.  Therefore, we should implement some batching for large
          sets.
  
          """
          threads = []
          results = []
  
          # Start the thread for each IP we wish to check.
          for count, ip in enumerate(list_of_ips):
              thread = threading.Thread(
                                  target = self._do_tcp_check,
                                  name   = "%s:%s" % (self.thread_name, ip),
                                  args   = (ip, results))
              thread.start()
              threads.append(thread)
  
          # ... make sure all threads are done...
          for thread in threads:
              thread.join()
  
          # ... and send back all the failed IPs.
          return results, []