public function createGroup($group_name, $role_name = 'Default')
 {
     if (trim($group_name) == "") {
         throw new e\CreationErrorException(S_SPAN . c\M::EMPTY_GROUP_NAME . E_SPAN);
     }
     $asset = AssetTemplate::getGroup();
     $asset->group->groupName = $group_name;
     $asset->group->role = $role_name;
     return $this->createAsset($asset, Group::TYPE, $group_name);
 }