code: function writeTopicConfig(client, topic, configs, callback) {
    debug('writeTopicConfig: "%s", %j', topic, configs);
    updateEntityConfig(client, getTopicConfigPath(topic), configs, callback);
  }
docs: Write out the topic config to zk, if there is any
  
  @param {ZkClient} client
  @param {String} topic
  @param {Object} configs
  @param {Function} callback