code: function Topic(name, account, region) {
              this._region = new AliMNS.Region(AliMNS.City.Hangzhou);
              this._pattern = "%s://%s.mns.%s.aliyuncs.com/topics/%s";
              this._name = name;
              this._account = account;
              // region
              if (region) {
                  if (typeof region === "string")
                      this._region = new AliMNS.Region(region, AliMNS.NetworkType.Public, AliMNS.Zone.China);
                  else
                      this._region = region;
              }
              // make url
              this._urlAttr = this.makeAttrURL();
              this._urlSubscription = this.makeSubscriptionURL();
              this._urlPublish = this.makePublishURL();
              // create the OpenStack object
              this._openStack = new AliMNS.OpenStack(account);
          }
docs: The constructor. name & account is required. region can be "hangzhou", "beijing" or "qingdao", the default is "hangzhou"