/**
* @param object $resource
* @param int $movement
*
* @return null|object
*/
public function move($resource, $movement)
{
$position = $this->config->getSortablePosition();
$accessor = PropertyAccess::createPropertyAccessor();
$accessor->setValue($resource, $position, $accessor->getValue($resource, $position) + $movement);
return $this->update($resource, 'move');
}
