public function isSubdomainExists( $subdomain, $excludeId = null )
    {
        return $this->isExists( empty( $excludeId ) ? array(
            'subdomain' => $subdomain,
        ) : array(
            'subdomain' => $subdomain,
            new Predicate\Operator(
                'id',
                Predicate\Operator::OP_NE,
                $excludeId
            ),
        ) );
    }