code: def get_min_isr(zk, topic):
      
      ISR_CONF_NAME = 'min.insync.replicas'
      try:
          config = zk.get_topic_config(topic)
      except NoNodeError:
          return None
      if ISR_CONF_NAME in config['config']:
          return int(config['config'][ISR_CONF_NAME])
      else:
          return None
docs: Return the min-isr for topic, or None if not specified