docs: function addonsManager_getAddonRadiogroup(aSpec) {
      var spec = aSpec || { };
      var addon = spec.addon;
      var radiogroup = spec.radiogroup;
  
      if (!radiogroup)
        throw new Error(arguments.callee.name + ": Radiogroup not specified.");
  
      return this.getAddonChildElement({addon: addon, type: radiogroup + "Radiogroup"});
    }