docs: def choice(self, subscribers, message):
          """
          Choose a random connection, favoring those that are reliable from
          subscriber pool to deliver specified message.
  
          @param subscribers: Collection of subscribed connections to destination. 
          @type subscribers: C{list} of L{coilmq.server.StompConnection}
  
          @param message: The message to be delivered. 
          @type message: L{stompclient.frame.Frame}
  
          @return: A random subscriber from the list or None if list is empty.
          @rtype: L{coilmq.server.StompConnection}
          """
          if not subscribers:
              return None
          reliable_subscribers = [
              s for s in subscribers if s.reliable_subscriber]
          if reliable_subscribers:
              return random.choice(reliable_subscribers)
          else:
              return random.choice(subscribers)