code: function genFunctionProxy(serviceName, methodName, origin, attach, proxyCB) {
      // logger.debug('rpc proxy genFunctionProxy serviceName : %s,methodName :%s', serviceName, methodName);
      return (() => {
          const proxy = (...args) => {
              logger.debug('rpc proxy args : %j', args);
              proxyCB(serviceName, methodName, args, attach);
          };
          proxy.toServer = (...args) => {
              logger.debug('rpc proxy toServer  args : %j', args);
              proxyCB(serviceName, methodName, args, attach, true);
          };
          return proxy;
      })();
  }
docs: Generate prxoy for function type field
  
  @param serviceName {String} delegated service name
  @param methodName {String} delegated method name
  @param origin {Object} origin object
  @param attach {Object} attach object
  @param proxyCB {Function} proxy callback function
  @returns function proxy