public function filterByUser($user, $comparison = null)
    {
        if ($user instanceof User) {
            return $this
                ->addUsingAlias(UserCustomerRelationPeer::USER_ID, $user->getId(), $comparison);
        } elseif ($user instanceof PropelObjectCollection) {
            if (null === $comparison) {
                $comparison = Criteria::IN;
            }

            return $this
                ->addUsingAlias(UserCustomerRelationPeer::USER_ID, $user->toKeyValue('PrimaryKey', 'Id'), $comparison);
        } else {
            throw new PropelException('filterByUser() only accepts arguments of type User or PropelCollection');
        }
    }