code: function (opts) {
          var objectGroupName = opts.name,
              objectGroup = null
  
          this.objectGroups.forEach(function (item) {
              if (item.name == objectGroupName) {
                  objectGroup = item
              }
          })
          if (objectGroup !== null) {
              return objectGroup
          }
      }
docs: Return the ObjectGroup for the secific group
  
  @opt {String} name The object group name
  @returns {cocos.TMXObjectGroup} The object group