def register_publisher(topic, topic_type)
      code, message, uris = @proxy.registerPublisher(@caller_id,
                                                     topic,
                                                     topic_type,
                                                     @slave_uri)
      if code == 1
        uris
      else
        raise message
      end
    end
def register_publisher(topic, topic_type)
      code, message, uris = @proxy.registerPublisher(@caller_id,
                                                     topic,
                                                     topic_type,
                                                     @slave_uri)
      if code == 1
        uris
      else
        raise message
      end
    end
register a publisher
 @param [String] topic topic name of topic
 @param [String] topic_type type of topic
 @return [Array] URI of current subscribers
 @raise RuntimeError