code: function(serviceName, methodName, origin, attach, proxyCB) {
    return (function() {
      let proxy = function() {
        // let args = arguments;
        let len = arguments.length;
        let args = new Array(len);
        for (let i = 0; i < len; i++) {
          args[i] = arguments[i];
        }
        // let args = Array.prototype.slice.call(arguments, 0);
        proxyCB(serviceName, methodName, args, attach);
      };
  
      proxy.toServer = function() {
        // let args = arguments;
        let len = arguments.length;
        let args = new Array(len);
        for (let i = 0; i < len; i++) {
          args[i] = arguments[i];
        }
        proxyCB(serviceName, methodName, args, attach, true);
      };
  
      return proxy;
    })();
  }
docs: Generate prxoy for function type field
  
  @param namespace {String} current namespace
  @param serverType {String} server type string
  @param serviceName {String} delegated service name
  @param methodName {String} delegated method name
  @param origin {Object} origin object
  @param proxyCB {Functoin} proxy callback function
  @returns function proxy