public function findByFilterComponentsFormatReturnValue( $qty, Container $output )
    {

        if( $qty === FindFilterComponentFactory::FIND_ALL ) {
            return $output;
        }

        switch( $count = count( $output ) ) {
            case 0:
                return null;
            case 1:
                return $output->pop();
        }

        throw new IncompatibleQtyException( "{$count} entities found - can't return 'one'" );

    }