/**
  * @return bool
  */
 public function deletePermission(User_ForgeUGroup $user_group, User_ForgeUserGroupPermission $permission)
 {
     $user_group_id = $user_group->getId();
     $permission_id = $permission->getId();
     return $this->permissions_dao->deletePersmissionForUGroup($user_group_id, $permission_id);
 }