public function filterByUser($user, $comparison = null)
    {
        if ($user instanceof \Alchemy\Component\Cerberus\Model\User) {
            return $this
                ->addUsingAlias(UserRoleTableMap::COL_USER_ID, $user->getId(), $comparison);
        } elseif ($user instanceof ObjectCollection) {
            if (null === $comparison) {
                $comparison = Criteria::IN;
            }

            return $this
                ->addUsingAlias(UserRoleTableMap::COL_USER_ID, $user->toKeyValue('PrimaryKey', 'Id'), $comparison);
        } else {
            throw new PropelException('filterByUser() only accepts arguments of type \Alchemy\Component\Cerberus\Model\User or Collection');
        }
    }